public override Node eval(Node t, Environment e)
{
if(t.getCdr() is Closure)
return e.lookup(t.getCar()).apply(t.getCdr());
else
{
Node args = t.getCdr();
Node param;
if (args.getCar().isSymbol())
param = new Cons(e.lookup((Node)args.GetCar()), Nil.getInstance());
else
param = new Cons((Node)args.GetCar(), Nil.getInstance());
Node currentNode = param;
args = args.getCdr();
while (args != Nil.getInstance())
{
if (args.getCar().isSymbol())
currentNode.setCdr(new Cons(e.lookup(args.getCar()), Nil.getInstance()));
else
currentNode.setCdr(new Cons(args.getCar(), Nil.getInstance()));
currentNode = currentNode.getCdr();
args = args.getCdr();
}
return e.lookup(t.getCar()).apply(param);
}
}
public override Node eval(Node exp, Environment env)
{
int length = Util.expLength(exp);
if (length < 3)
{
Console.Error.WriteLine("Error: invalid expression");
return Nil.getInstance();
}
Node second = exp.getCdr().getCar();
Node name, value;
if (length == 3 && second.isSymbol())
{
name = second;
value = exp.getCdr().getCdr().getCar().eval(env);
env.define(name, value);
return null;
}
if (!second.isPair())
{
Console.Error.WriteLine("Error: invalid expression");
return Nil.getInstance();
}
name = second.getCar();
Node lambda = exp.getCdr();
lambda.setCar(second.getCdr());
lambda = new Cons(new Ident("lambda"), lambda);
value = lambda.eval(env);
env.define(name, value);
return null;
}
public Node evalLetBody(Node t, Environment env)
{
if(t == Nil.getInstance()) //This isn't correct. What do?
{
Node l = new Cons(new Nil(), new Nil()); //tree with pair of ()
return l;
}
else
{
Node restBody = t.getCdr();
Node variable = t.getCar().getCar();
Node value = t.getCar().getCdr().getCar();
if(variable.isSymbol()) //was value earlier, should be variable?
{
env.define(variable,value.eval(env));
return evalLetBody(restBody, env);
}
else if(!variable.isPair()) //if it is a cons node. ???
{
Console.Write("Error in Let->evalLetBody, variable is not valid");
return new Nil();
}
else if(variable.isNull())
{
return new Nil();
}
else
{
return variable.eval(env);
}
}
}
// TODO: The method apply() should be defined in class Node
// to report an error. It should be overridden only in classes
// BuiltIn and Closure.
public override Node apply(Node args)
{
Environment funcEnvironment = new Environment(env);
Node param = fun.getCdr().getCar();
while (param != Nil.getInstance() && args != Nil.getInstance())
{
funcEnvironment.define(param.getCar(), args.getCar());
param = param.getCdr();
args = args.getCdr();
}
Node body = new Cons(new Ident("begin"), fun.getCdr().getCdr());
return body.eval(funcEnvironment);
}
public override Node eval(Environment env, Node args)
{
// Evaluate the list
Node evaluated = new Cons(args.getCar().eval(env), args.getCdr().eval(env));
// If the car is a closure, apply it
if (evaluated.getCar().isProcedure())
{
return(evaluated.getCar().apply(evaluated.getCdr()));
}
else
{
return(evaluated);
}
}
public override Node apply(Node args)
{
Environment funcEnv = new Environment(env);
Node temp = fun.getCdr().getCar();
while (temp != Nil.getInstance())
{
funcEnv.define(temp.getCar(), args.getCar());
temp = temp.getCdr();
args = args.getCdr();
}
Node body = new Cons(new Ident("begin"), fun.getCdr().getCdr());
return(body.eval(funcEnv));
}
public void assign(Node id, Node val)
{
// search for id in id_value_pair in frame heirarchy
Node result_lookup = lookup(id);
// if nothing found, report error.
if (result_lookup == null)
{
Console.Error.WriteLine("Exception in assigning: variable with that name does not exist");
}
else
{
result_lookup = new Cons(val, Nil.getInstance());
}
}
public override Node eval(Node t, Environment env)
{
Node variable = t.getCdr().getCar();
if(variable.isPair())
{
//variable is of the form (decl params...), ex: (foo x y)
Node declaration = variable.getCar();
Node parameters = variable.getCdr();
Cons lambda = new Cons(new Ident("lambda"),new Cons(parameters,t.getCdr().getCdr().getCar()));
env.define(declaration,new Closure(lambda, env));
}
else
{
env.define(variable, t.getCdr().getCdr().getCar().eval(env));
}
return new StringLit("definition recorded");
}
public override Node eval(Node t, Environment env)
{
Node car1 = t.getCdr().getCar();
Node car2 = t.getCdr().getCdr().getCar();
if (car1.isSymbol())
{
// if first arg is not a list, define variable
env.define(car1, car2);
}
else
{
// if first arg is list, define function and function body
Cons funcbody = new Cons(car1.getCdr(), t.getCdr().getCdr());
Node closureFun = new Cons(new Ident("lambda"), funcbody).eval(env);
env.define(car1.getCar(), closureFun);
}
return(Void.getInstance());
}
public override Node eval(Node exp, Environment env)
{
int numArgs = 0;
Node expCdr = exp.getCdr();
while (!expCdr.isNull())
{
numArgs++;
expCdr = expCdr.getCdr();
}
if (numArgs < 2)
{
Console.Error.WriteLine("Error: invalid expression");
return(Nil.getInstance());
}
Node arg1 = exp.getCdr().getCar();
if (numArgs == 2 && arg1.isSymbol())
{
Node val = exp.getCdr().getCdr().getCar();
env.define(arg1, val.eval(env));
return(new StringLit("; no values returned", false));
}
if (arg1.isPair())
{
Node fName = arg1.getCar();
Node fArgs = arg1.getCdr();
Node fBody = exp.getCdr().getCdr();
bool validArgs = verifyArgs(fArgs);
if (fName.isSymbol() && validArgs)
{
Node node = new Cons(new Ident("lambda"), new Cons(fArgs, fBody));
env.define(fName, node.eval(env));
return(new StringLit("; no values returned", false));
}
Console.Error.WriteLine("Error: ill-formed definition");
return(Nil.getInstance());
}
Console.Error.WriteLine("Error: invalid expression");
return(Nil.getInstance());
}
public override Node eval(Environment env, Node args)
{
Node expr1 = args.getCar();
if (args.getCdr().isNull() == true)
{
return(new StringLit("Error: Only 1 argument passed to 'define.'"));
}
else if (args.getCdr().getCdr().isNull() == false)
{
return(new StringLit("Error: Too many arguments passed to 'define.'"));
}
// Is this defining a function?
else if (expr1.isPair() == true)
{
if (expr1.getCar().isSymbol() == true)
{
// Construct the lambda expression
Node formalsAndBody = new Cons(expr1.getCdr(), args.getCdr());
Node lambdaExpr = new Cons(new Ident("lambda"), formalsAndBody);
// define.apply()
return(env.define(expr1.getCar(), lambdaExpr.eval(env)));
}
else
{
return(new StringLit("Error: First argument to 'define' must be a <variable>"));
}
}
else
{
if (expr1.isSymbol() == true)
{
// define.apply()
return(env.define(expr1, args.getCdr().getCar().eval(env)));
}
else
{
return(new StringLit("Error: First argument to 'define' must be a <variable>"));
}
}
}
public Node evalRest(Node t, Environment env)
{
Node c;
if(t == null)
{
c = new Cons(new Nil(), new Nil());
}
else
{
Node car = t.getCar();
Node cdr = t.getCdr();
if(car.isSymbol())
{
car = env.lookup(car);
}
c = new Cons(car.eval(env), evalRest(cdr, env));
return c;
}
return c;
}
public override Node eval(Node t, Environment env)
{
// if cdr is null, define call has no arguments (error state)
if (t.getCdr() == Nil.getInstance())
{
Console.Error.WriteLine("Special form 'Define' evaluated with no arguments");
return(Nil.getInstance());
}
// to evaluate an expression of the form '(eval x e)',
// evaluate e, store its value as e1, then look up x in the current scope.
// if a binding for x exists, set the value to e1
// otherwise, add (x e1) as the first element of the first association
// lists into env.
t = t.getCdr();
// determine if the form is '(eval x e)'
if (t.getCar().isSymbol())
{
// evaluate e, then store into e1
Node e1 = t.getCdr().eval(env);
env.define(t.getCar(), e1);
}
// if the expression is of the form '(define (x p1 ... pn) b1 ... bm)',
// construct the lambda expression
// (lambda(p1...pn) b1...bm)
// then proceed as for the definition
// (define x(lambda(p1...pn) b1...bm))
if (t.getCar().isPair())
{
Node arg1 = t.getCar().getCar();
Cons arg2 = new Cons(new Ident("lambda"), new Cons(t.getCdr().getCar(), t.getCdr().getCar().getCdr()));
env.define(arg1, arg2);
}
return(null);
}
public void define(Node id, Node val)
{
// it should be noted that when parsing the written structure
// print elements,... if there is a left parenthesis in front
// in front of variable name, ... we are dealing with a function definition.
//
// and the variable name ought to be considered an identifier.
// function example : where root cons node is given by: identifier
// a .
// a equals : (define (xoo x) (+ x x))
// to get expression for lambda out of any function defintion...
// node funcLambda = (cons 'lambda (cons (cdr (car (cdr a))) (cdr (cdr a))))
// xoo can be looked up by querying: (car (car (cdr a)))
// we only want to define this in the frontmost frame at hand.
Node result_lookup = find(id, frame.get_root_of_frame());
if (result_lookup == null)
{
Cons node_being_added = new Cons(id, new Cons(val, Nil.getInstance()));
// put new definition in front of frame ( association list structure )
frame.set_root_car_node(node_being_added);
}
else
// if preexisting...
// update node for value (, in innermost scope).
{
result_lookup = new Cons(val, Nil.getInstance());
}
}
// to evaluate expressions of the regular form '(f a1 ... an)',
// i.e. function calls that don't fit under another Special
// subclass, recursively evaluate f, a1, ... an, calling the
// results f', a1', ... an', then call apply with f' as the
// first argument, and (a1', ... an') as the second argument.
public override Node eval(Node t, Environment env)
{
// get f' from t to use for apply call later.
Node fPrime = t.getCar().eval(env);
// create node for holding list (a1' ... an')
Node aPrime = Nil.getInstance();
// get cdr of regular (a1 ... an)
t = t.getCdr();
// recursively evaluate a1 ... a(n-1)
while (t.getCdr() != Nil.getInstance())
{
aPrime = new Cons(aPrime, t.getCar().eval(env));
t = t.getCdr();
}
// evaluate an, add to list, and return a'
aPrime = new Cons(aPrime, t.getCar().eval(env));
return(fPrime.apply(aPrime));
}
public Node define(Node id, Node val)
{
Node oldVal = find(id, frame);
if (oldVal != null)
{
// id exists in environment, update the value
oldVal.setCar(val);
return(new StringLit("no values returned."));
}
else
{
// Add the new frame to the environment (front of the association list)
Node newFrame = new Cons(new Cons(id, new Cons(val, null)), null); // New variable for clarity
newFrame.setCdr(frame);
frame = newFrame;
return(new StringLit("no values returned."));
}
}
public override Node eval(Node t, Environment env)
{
Node iden = t.getCdr().getCar();
Node val = t.getCdr().getCdr().getCar();
if (iden.isSymbol())
{
env.define(iden, val);
}
else
{
Closure close = new Closure(new Cons(t.getCdr().getCar().getCdr(), t.getCdr().getCdr()), env);
env.define(iden.getCar(), close);
}
if (iden.isPair())
{
Node func = iden.getCar();
Cons list = new Cons(new Ident("lambda"), new Cons(val, t.getCdr().getCar().getCdr()));
env.define(func, list);
}
return(new StringLit("Values are null (Define)"));
}
public Node evalRegList(Node t, Environment env)
{
if (t == null || t.isNull())
{
Node list = new Cons(Nil.getInstance(), Nil.getInstance());
return(list);
}
else
{
Node arg = t.getCar();
Node rest = t.getCdr();
if (arg.isSymbol())
{
arg = env.lookup(arg);
}
if (arg == null || arg.isNull())
{
return(Nil.getInstance());
}
Node list = new Cons(arg.eval(env), evalRegList(rest, env));
return(list);
}
}
// sets first as function, args as function arguments, and performs apply() on first
public override Node eval(Node t, Environment env)
{
Node first = t.getCar();
Node args = t.getCdr();
if (!(args is Nil))
{
if (t.getCdr().getCar().isSymbol())
{
args = getArgs(t.getCdr(), env);
}
if (t.getCdr().getCar().isPair() && !t.getCdr().getCar().getCar().isNumber())
{
args = new Cons(t.getCdr().getCar().eval(env), Nil.getInstance());
}
if (env.lookup(first).isProcedure())
{
first = env.lookup(first);
Node temp = first.apply(args);
return(temp);
}
else
{
Console.WriteLine("Error: Procedure not specified.");
}
}
else
{
if (env.lookup(first).isProcedure())
{
first = env.lookup(first);
Node temp = first.apply(Nil.getInstance());
return(temp);
}
}
return(Void.getInstance());
}
// also now need to ensure that all arguments in regular expression
// get their values looked up if they are symbols
// implementation
// Note : sometimes env1 will not conform, or be pertinent to what is written relation to c# loops and scheme code
public override Node eval(Node node1, Environment env1)
{
if (node1 == null || node1.getCar() == null)
{
Console.WriteLine("Error: the expression is not initialized to values: null list and car");
return(Nil.getInstance());
}
// for any regular defined function enclosed in parentheses,
// the first element is supposed to be a function to be evaluated.
// this variable will hold the final function head term we get.
Node firstElem_car = node1.getCar();
// step one : if Car is a pair, evaluate it and store resulting ident, ... which ought to be
// another function once evaluated...
if (node1.getCar().isPair())
{
// build new environment for this to be computed for.
Environment envExtend = new Environment(env1);
firstElem_car = node1.getCar().eval(envExtend);
//report error if not a builtin/ or /closure
if (firstElem_car == null || !firstElem_car.isProcedure())
{
Console.WriteLine("Error: regular expression needs a function builtin/closure for first term!, __ + returning null instead.");
return(Nil.getInstance());
}
}
else if (node1.getCar().isSymbol())
{
// start loop to get closure from obstructing intermediate symbolic expression.
bool first_element_is_not_closure = true;
firstElem_car = node1.getCar();
while (first_element_is_not_closure)
{
firstElem_car = env1.lookup(firstElem_car);
//report error if not a builtin/ or /closure
if (firstElem_car == null)
{
Console.WriteLine("Error: regular expression needs a function builtin/closure for first term!, __ + returning null instead.");
return(Nil.getInstance());
}
else if (firstElem_car.isProcedure())
{
first_element_is_not_closure = false;
}
}
}
// this would be improper end for cons regular expression.
if (node1.getCdr() == null)
{
Console.WriteLine("error: one of regular expressions elements is null.");
return(Nil.getInstance());
}
// special builtIn eval case.
BuiltIn givenId = null;
if (firstElem_car.isBuiltIn())
{
givenId = (BuiltIn)firstElem_car;
// check if built in is eval
// note carefully: if symbol == null, null pointer will happen.
if (givenId.getSymbol().getName().Equals("eval"))
{
// build new environment for this to be computed for.
Environment envExtend = new Environment(env1);
// check for null values now so null pointer doesnt get encountered
if (node1.getCdr().getCar() == null || node1.getCdr().getCdr() == null ||
node1.getCdr().getCdr().getCar() == null)
{
Console.WriteLine("Error: lacking one of the following for eval : expression or environment.");
return(Nil.getInstance());
}
// side maneuver. _ work out the environment first...
bool environment_taken = false;
Node env_symbol_to_lookup = node1.getCdr().getCdr().getCar();
Node environment_found = null;
// check if symbol needs to be evaluated
if (env_symbol_to_lookup.isSymbol())
{
if (env1.lookup(env_symbol_to_lookup) != null)
{
environment_found = env1.lookup(env_symbol_to_lookup);
}
else
{
Console.WriteLine("Error: environment symbol was not found.");
return(Nil.getInstance());
}
} // check if expression needs to be evaluated
else if (env_symbol_to_lookup.isPair())
{
environment_found = env_symbol_to_lookup.eval(envExtend);
}
if (environment_found != null && environment_found.isEnvironment())
{
environment_taken = true;
}
else
{
Console.WriteLine("Error: evaluation op_ did not find a fitting environment.");
return(Nil.getInstance());
}
// working on expression now
Node args_to_eval = null;
Node localTerms_data = node1.getCdr().getCar();
// check if second argument is code
// and then evaluate if it needs more processing
// for eval to implement as code
if (localTerms_data.isPair() && environment_taken)
{
if (localTerms_data.getCar() != null && localTerms_data.getCar().isSymbol() &&
localTerms_data.getCar().getName().Equals("quote"))
{
Node args_of_Quote = localTerms_data.eval(envExtend);
if (args_of_Quote != null)
{
// copy evaluated quote expression
args_to_eval = args_of_Quote;
}
}
else if (localTerms_data.getCar() != null && localTerms_data.getCar().isSymbol() &&
localTerms_data.getCar().getName().Equals("lambda"))
{
Node args_of_Lambda = localTerms_data.eval(envExtend);
if (args_of_Lambda != null)
{
// copy evaluated lambda expression
args_to_eval = args_of_Lambda;
}
}
else
{
// this needs fine tuning for more special cases..\\
//("may have more cases... ")
//??
args_to_eval = localTerms_data;
}
}
else if (localTerms_data.isSymbol() && environment_taken)
{
Node node_symbol_expression = env1.lookup(localTerms_data);
if (node_symbol_expression != null)
{
// copy evaluated symbol and then the environment
args_to_eval = node_symbol_expression;
}
else
{
Console.WriteLine("Error: first expression argument symbol not found.");
return(Nil.getInstance());
}
}
// return the built in eval of args and environment given
if (args_to_eval != null)
{
Environment environment_copy_found = (Environment)environment_found;
if (args_to_eval.isPair())
{
return(args_to_eval.eval(environment_copy_found));
}
else
{
return(args_to_eval.eval(environment_copy_found));
}
}
else
{
Console.WriteLine("Error: expression arg was null.");
return(Nil.getInstance());
}
}
// note: looking at special eq? case
// check if built in is eq? only look at case of (eq? 'exp 'exp)
// note carefully: if symbol == null, null pointer will happen.
if (givenId.getSymbol().getName().Equals("eq?") &&
node1.getCdr().getCar() != null &&
node1.getCdr().getCdr() != null &&
node1.getCdr().getCdr().getCar() != null &&
node1.getCdr().getCdr().getCdr() != null &&
node1.getCdr().getCdr().getCdr().isNull() &&
node1.getCdr().getCar().isPair() &&
node1.getCdr().getCdr().getCar().isPair()
)
{
// first we must check if the arguments to (eq? ... )are in fact quote arguments.
Cons argument1 = (Cons)node1.getCdr().getCar();
Cons argument2 = (Cons)node1.getCdr().getCdr().getCar();
if (argument1.getForm_ofCons() is Tree.Quote && argument2.getForm_ofCons() is Tree.Quote)
{
String first_argument_printed = "";
String second_argument_printed = "";
// redirect output to evaulate if print of Pair nodes is same
var originalConsoleOut = Console.Out; // preserve the original stream
using (var writer = new StringWriter())
{
Console.SetOut(writer);
argument1.print(0);
writer.Flush();
var myString = writer.ToString();
first_argument_printed = myString.TrimEnd('\n');
}
using (var writer1 = new StringWriter())
{
Console.SetOut(writer1);
argument2.print(0);
writer1.Flush();
var myString_2 = writer1.ToString();
second_argument_printed = myString_2.TrimEnd('\n');
}
Console.SetOut(originalConsoleOut); // restore Console.Out
if (first_argument_printed.Equals(second_argument_printed))
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
}
// security check for eof-object? builtIn test...
if (givenId != null && givenId.getSymbol().getName().Equals("eof-object?"))
{
if (node1.getCdr().isNull() || !node1.getCdr().isPair())
{
Console.WriteLine("Error: no argument for eof-object? test. the BuiltIn function eof-object? requires one argument to test.");
return(Nil.getInstance());
}
}
}
// other cases builtin or closure...
Node args_given = node1.getCdr();
bool hasArguments = true;
// test if there are arguments to this form function
if (args_given.isNull())
{
hasArguments = false;
}
if (hasArguments)
{
if (args_given.getCdr() == null || args_given.getCar() == null)
{
Console.WriteLine("Error: one of passed arguments in function expression is null.");
return(Nil.getInstance());
}
// need to evaluate args (each car separately)... and then return what is resulting list of elements...
// build new environment on hand _ for each car to be computed at times.
Environment envExtend1 = new Environment(env1);
// this will hold the list of evaluated arguments cumulatively.
Cons evaluated_argsList__in_progress;
// this will hold a latest fringe of for extending fringe items.
Cons fringe_cons = null;
bool hasMoreDescendents = !args_given.getCdr().isNull();
if (hasMoreDescendents)
{
// start this off as unassigned.
Cons added_fringe_con = null;
// this will hold the list of evaluated arguments cumulatively.
// Cons evaluated_argsList__in_progress;
// check if eval is not null
Node evalItem1 = args_given.getCar().eval(envExtend1);
if (evalItem1 != null)
{
evaluated_argsList__in_progress = new Cons(evalItem1, added_fringe_con);
}
else
{
// first a detour...
//
// check for special case of eof-object? builtIn test
if (givenId != null && givenId.getSymbol().getName().Equals("eof-object?"))
{
Console.WriteLine("Error: too many args for function eof-object? test. ");
return(Nil.getInstance());
} // normal case where regular expression argument evaluated to null is to throw an error
else
{
Console.WriteLine("Error: one of the args items in regular function was null. ");
return(Nil.getInstance());
}
}
// under the alias of fringe_cons...
// we will continue this reference down to assess the next fringe branch
fringe_cons = evaluated_argsList__in_progress;
}
// dealt with the sole generation here.
// no more fringes left.
else
{
// check if eval is not null
Node evalItem1 = args_given.getCar().eval(envExtend1);
if (evalItem1 != null)
{
// first a detour...
//
// check for special case of eof-object? builtIn test is false
if (givenId != null && givenId.getSymbol().getName().Equals("eof-object?"))
{
return(BoolLit.getInstance(false));
} // normal case where regular expression argument evaluated to null is to throw an error
else
{
evaluated_argsList__in_progress = new Cons(evalItem1, Nil.getInstance());
}
}
else
{
// first a detour...
//
// check for special case of eof-object? builtIn test is true
if (givenId != null && givenId.getSymbol().getName().Equals("eof-object?"))
{
return(BoolLit.getInstance(true));
} // normal case where regular expression argument evaluated to null is to throw an error
else
{
Console.WriteLine("Error: the sole additional argument item in regular function was null. ");
return(Nil.getInstance());
}
}
}
// done with first step in two levels descendents
// get rest of fringes
while (hasMoreDescendents)
{
if (args_given.getCdr() == null)
{
Console.WriteLine("Error: one of the later argument items in regular function was null. ");
return(Nil.getInstance());
}
// precaution for null pointer so it is legal to use the cdr after this test
if (args_given.getCdr().isPair())
{
// build new environment for this to be computed for.
Environment envExtend2 = new Environment(env1);
// get next fringe descendent.
args_given = args_given.getCdr();
// start this off as unassigned.
Cons added_fringe_con = null;
// check if additional eval items are not null
Node evalItem_more = args_given.getCar().eval(envExtend2);
if (evalItem_more != null)
{
fringe_cons.setCdr(new Cons(evalItem_more, added_fringe_con));
}
else
{
Console.WriteLine("Error: one of the later argument items in regular function was null. ");
return(Nil.getInstance());
}
fringe_cons = (Cons)fringe_cons.getCdr();
}
else if (args_given.getCdr().isNull())
{
fringe_cons.setCdr(Nil.getInstance());
hasMoreDescendents = false;
}
else
{
// build new environment for this to be computed for.
Environment envExtend2 = new Environment(env1);
// get one remaining fringe descendent.
args_given = args_given.getCdr();
// check if additional eval items are not null
Node evalItem_more = args_given.getCar().eval(envExtend2);
if (evalItem_more != null)
{
fringe_cons.setCdr(new Cons(evalItem_more, Nil.getInstance()));
}
else
{
Console.WriteLine("Error: one of the later argument items in regular function was null. ");
return(Nil.getInstance());
}
hasMoreDescendents = false;
}
}
return(firstElem_car.apply(evaluated_argsList__in_progress));
}
return(firstElem_car.apply(Nil.getInstance()));
}
// TODO: The method apply() should be defined in class Node
// to report an error. It should be overridden only in classes
// BuiltIn and Closure.
public override Node apply(Node args)
{
// note for all built in functions that need arguments...
//
// the function will never do a test to check whether args is a pair, because
// args is always made a pair in special Regular for launching builtin_function apply.
if (this.symbol.getName().Equals("read"))
{
if (args == null || !args.isNull())
{
Console.WriteLine("Error: Read only needs no arguments for use.");
return(Nil.getInstance());
}
return((Node)Scheme4101.parser.parseExp());
}
else if (this.symbol.getName().Equals("write"))
{
if (args == null || args.isNull())
{
Console.WriteLine("Error: incorrect arguments. Nil passed, which cannot be used.");
return(Nil.getInstance());
}
args.getCar().print(0);
return(Nil.getInstance());
}
else if (this.symbol.getName().equals("set-car!"))
{
arg1.setCar(arg2);
return(arg1);
}
else if (this.symbol.getName().equals("set-cdr!"))
{
arg1.setCdr(arg2);
return(arg1);
}
else if (this.symbol.getName().Equals("display"))
{
if (args == null || args.isNull())
{
Console.WriteLine("Error: incorrect arguments. Nil passed, which cannot be used.");
return(Nil.getInstance());
}
Tree.BuiltIn.builtIn_display__do_not_print_double_quotes = true;
args.getCar().print(0);
Tree.BuiltIn.builtIn_display__do_not_print_double_quotes = false;
return(Nil.getInstance());
}
else if (this.symbol.getName().Equals("b+"))
{
// if there are no arguments, report error
if (args == null)
{
Console.WriteLine("Error: no arguments given for binary addition operation.");
return(Nil.getInstance());
}
// return zero if there are no arguments
if (args.isNull())
{
return(new IntLit(0));
}
// extend for all argument vars
// and
//check if first args have null
if (args.getCar() != null &&
args.getCdr() != null)
{
bool twoArguments_or_more;
// check if second argument is is nil.
if (args.getCdr().isNull())
{
twoArguments_or_more = false;
}
// see if there is a second item , ... and check that last tail of args is nil.
else if (args.getCdr().getCar() != null && args.getCdr().getCdr().isNull())
{
twoArguments_or_more = true;
}
else if (args.getCdr().getCar() != null && !args.getCdr().getCdr().isNull())
{
Console.WriteLine("Error: cannot process more than two args for binary addition.");
return(Nil.getInstance());
}
else
{
Console.WriteLine("Error: in b+ , one of arguments for expression has null node.");
return(Nil.getInstance());
}
if (twoArguments_or_more == false)
{
// check if argument is an intLit
if (args.getCar().isNumber())
{
// return the sole int lit node.
return(args.getCar());
}
else
{
Console.WriteLine("Error: in b+ , one of arguments for expression has null node.");
return(Nil.getInstance());
}
}
else
{
if (!args.getCar().isNumber() || !args.getCdr().getCar().isNumber())
{
Console.WriteLine("Error: arguments must be IntLit for binary addition.");
return(Nil.getInstance());
}
else
{
IntLit int1 = (IntLit)args.getCar();
IntLit int2 = (IntLit)args.getCdr().getCar();
return(new IntLit(int1.getInt() + int2.getInt()));
}
}
}
else
{
Console.WriteLine("Error: in b+ , there is a null external node");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("b-"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for binary subtraction operation.");
return(Nil.getInstance());
}
// extend for all argument vars
// and
//check if any args have null or nil.
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().getCar() != null &&
args.getCdr().getCdr().isNull())
{
if (!args.getCar().isNumber() || !args.getCdr().getCar().isNumber())
{
Console.WriteLine("Error: arguments must be IntLit for binary subtraction.");
return(Nil.getInstance());
}
else
{
IntLit int1 = (IntLit)args.getCar();
IntLit int2 = (IntLit)args.getCdr().getCar();
return(new IntLit(int1.getInt() - int2.getInt()));
}
}
else
{
Console.WriteLine("Error: more than two arguments for binary subtraction is not permissable.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("b*"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for binary multiplication operation.");
return(Nil.getInstance());
}
// extend for all argument vars
// and
//check if any args have null or nil.
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().getCar() != null &&
args.getCdr().getCdr().isNull())
{
if (!args.getCar().isNumber() || !args.getCdr().getCar().isNumber())
{
Console.WriteLine("Error: arguments must be IntLit for binary multiplication.");
return(Nil.getInstance());
}
else
{
IntLit int1 = (IntLit)args.getCar();
IntLit int2 = (IntLit)args.getCdr().getCar();
return(new IntLit(int1.getInt() * int2.getInt()));
}
}
else
{
Console.WriteLine("Error: more than two arguments for binary multiplication is not permissable.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("b/"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for binary division operation.");
return(Nil.getInstance());
}
// extend for all argument vars
// and
//check if any args have null or nil.
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().getCar() != null &&
args.getCdr().getCdr().isNull())
{
if (!args.getCar().isNumber() || !args.getCdr().getCar().isNumber())
{
Console.WriteLine("Error: arguments must be IntLit for binary division.");
return(Nil.getInstance());
}
else
{
IntLit int1 = (IntLit)args.getCar();
IntLit int2 = (IntLit)args.getCdr().getCar();
if (int2.getInt() == 0)
{
Console.WriteLine("Error: input not acceptable. cannot divide by zero.");
return(Nil.getInstance());
}
else
{
return(new IntLit(int1.getInt() / int2.getInt()));
}
}
}
else
{
Console.WriteLine("Error: more than two arguments for binary division is not permissable.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("b="))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for binary equality test operation.");
return(Nil.getInstance());
}
// extend for all argument vars
// and
//check if any args have null or nil.
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().getCar() != null &&
args.getCdr().getCdr().isNull())
{
if (!args.getCar().isNumber() || !args.getCdr().getCar().isNumber())
{
Console.WriteLine("Error: arguments must be IntLit for binary equality test.");
return(Nil.getInstance());
}
else
{
IntLit int1 = (IntLit)args.getCar();
IntLit int2 = (IntLit)args.getCdr().getCar();
bool resultOfTest = (int1.getInt() == int2.getInt());
if (resultOfTest)
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
}
else
{
Console.WriteLine("Error: more than two arguments for binary equality test is not permissable.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("b<"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for binary less than test operation.");
return(Nil.getInstance());
}
// extend for all argument vars
// and
//check if any args have null or nil.
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().getCar() != null &&
args.getCdr().getCdr().isNull())
{
if (!args.getCar().isNumber() || !args.getCdr().getCar().isNumber())
{
Console.WriteLine("Error: arguments must be IntLit for binary less than test.");
return(Nil.getInstance());
}
else
{
IntLit int1 = (IntLit)args.getCar();
IntLit int2 = (IntLit)args.getCdr().getCar();
bool resultOfTest = (int1.getInt() < int2.getInt());
if (resultOfTest)
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
}
else
{
Console.WriteLine("Error: more than two arguments for binary less than test is not permissable.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("b>"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for binary greater than test operation.");
return(Nil.getInstance());
}
// extend for all argument vars
// and
//check if any args have null or nil.
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().getCar() != null &&
args.getCdr().getCdr().isNull())
{
if (!args.getCar().isNumber() || !args.getCdr().getCar().isNumber())
{
Console.WriteLine("Error: arguments must be IntLit for binary greater than test.");
return(Nil.getInstance());
}
else
{
IntLit int1 = (IntLit)args.getCar();
IntLit int2 = (IntLit)args.getCdr().getCar();
bool resultOfTest = (int1.getInt() > int2.getInt());
if (resultOfTest)
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
}
else
{
Console.WriteLine("Error: more than two arguments for binary greater than test is not permissable.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("b<="))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for binary less than equal than test operation.");
return(Nil.getInstance());
}
// extend for all argument vars
// and
//check if any args have null or nil.
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().getCar() != null &&
args.getCdr().getCdr().isNull())
{
if (!args.getCar().isNumber() || !args.getCdr().getCar().isNumber())
{
Console.WriteLine("Error: arguments must be IntLit for binary less than equal than test.");
return(Nil.getInstance());
}
else
{
IntLit int1 = (IntLit)args.getCar();
IntLit int2 = (IntLit)args.getCdr().getCar();
bool resultOfTest = (int1.getInt() <= int2.getInt());
if (resultOfTest)
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
}
else
{
Console.WriteLine("Error: more than two arguments for binary less than equal than test is not permissable.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("b>="))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for binary greater than equal than test operation.");
return(Nil.getInstance());
}
// extend for all argument vars
// and
//check if any args have null or nil.
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().getCar() != null &&
args.getCdr().getCdr().isNull())
{
if (!args.getCar().isNumber() || !args.getCdr().getCar().isNumber())
{
Console.WriteLine("Error: arguments must be IntLit for binary greater than equal than test.");
return(Nil.getInstance());
}
else
{
IntLit int1 = (IntLit)args.getCar();
IntLit int2 = (IntLit)args.getCdr().getCar();
bool resultOfTest = (int1.getInt() >= int2.getInt());
if (resultOfTest)
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
}
else
{
Console.WriteLine("Error: more than two arguments for binary greater than equal than test is not permissable.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("null?"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for testing null evaluation.");
return(Nil.getInstance());
}
// extend for all argument vars
// check if number of args is correct
bool argument_number_good = false;
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().isNull())
{
argument_number_good = true;
}
if (argument_number_good)
{
if (args.getCar().isNull())
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
else
{
Console.WriteLine("Error: wrong number of arguments for test. only need 1 cons node with nil tail for argument.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("symbol?"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for testing symbol evaluation.");
return(Nil.getInstance());
}
// extend for all argument vars
// check if number of args is correct
bool argument_number_good = false;
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().isNull())
{
argument_number_good = true;
}
if (argument_number_good)
{
if (args.getCar().isSymbol())
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
else
{
Console.WriteLine("Error: wrong number of arguments for test. only need 1 cons node with nil tail for argument.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("number?"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for testing number evaluation.");
return(Nil.getInstance());
}
// extend for all argument vars
// check if number of args is correct
bool argument_number_good = false;
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().isNull())
{
argument_number_good = true;
}
if (argument_number_good)
{
if (args.getCar().isNumber())
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
else
{
Console.WriteLine("Error: wrong number of arguments for test. only need 1 cons node with nil tail for argument.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("boolean?"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for testing boolean evaluation.");
return(Nil.getInstance());
}
// extend for all argument vars
// check if number of args is correct
bool argument_number_good = false;
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().isNull())
{
argument_number_good = true;
}
if (argument_number_good)
{
if (args.getCar().isBool())
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
else
{
Console.WriteLine("Error: wrong number of arguments for test. only need 1 cons node with nil tail for argument.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("procedure?"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for testing procedure evaluation.");
return(Nil.getInstance());
}
// extend for all argument vars
// check if number of args is correct
bool argument_number_good = false;
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().isNull())
{
argument_number_good = true;
}
if (argument_number_good)
{
if (args.getCar().isProcedure())
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
else
{
Console.WriteLine("Error: wrong number of arguments for test. only need 1 cons node with nil tail for argument.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("pair?"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for testing pair evaluation.");
return(Nil.getInstance());
}
// extend for all argument vars
// check if number of args is correct
bool argument_number_good = false;
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().isNull())
{
argument_number_good = true;
}
if (argument_number_good)
{
if (args.getCar().isPair())
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
else
{
Console.WriteLine("Error: wrong number of arguments for test. only need 1 cons node with nil tail for argument.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("environment?"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for testing environment evaluation.");
return(Nil.getInstance());
}
// extend for all argument vars
// check if number of args is correct
bool argument_number_good = false;
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().isNull())
{
argument_number_good = true;
}
if (argument_number_good)
{
if (args.getCar().isEnvironment())
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
else
{
Console.WriteLine("Error: wrong number of arguments for test. only need 1 cons node with nil tail for argument.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("string?"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for testing string evaluation.");
return(Nil.getInstance());
}
// extend for all argument vars
// check if number of args is correct
bool argument_number_good = false;
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().isNull())
{
argument_number_good = true;
}
if (argument_number_good)
{
if (args.getCar().isString())
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
else
{
Console.WriteLine("Error: wrong number of arguments for test. only need 1 cons node with nil tail for argument.");
return(Nil.getInstance());
}
}
// working on predicate built in : eq?
else if (this.symbol.getName().Equals("eq?"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for eq? test operation.");
return(Nil.getInstance());
}
// extend for all argument vars
// and
//check if any args have null or nil.
if (args != null && args.getCar() != null &&
args.getCdr() != null && args.getCdr().getCar() != null &&
args.getCdr().getCdr().isNull())
{
//if (!args.getCar () || !args.getCdr ().getCar () )
// check nil/null? first
// first car is nil but second item is not nil...
// or the other way around (vice versa)
if ((args.getCar().isNull() && !args.getCdr().getCar().isNull()) ||
(!args.getCar().isNull() && args.getCdr().getCar().isNull()))
{
return(BoolLit.getInstance(false));
}
// success: both nil
else if (args.getCar().isNull() && args.getCdr().getCar().isNull())
{
return(BoolLit.getInstance(true));
}
// first car is type symbol but second item is not symbol...
// or the other way around (vice versa)
else if ((args.getCar().isSymbol() && !args.getCdr().getCar().isSymbol()) ||
(!args.getCar().isSymbol() && args.getCdr().getCar().isSymbol()))
{
return(BoolLit.getInstance(false));
}
// check if both symbol now...
else if (args.getCar().isSymbol() && args.getCdr().getCar().isSymbol())
{
// check if the symbol's are identical
if (args.getCar().getName().Equals(args.getCdr().getCar().getName()))
{
// success: both same symbol!
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
// first car is type number but second item is not number...
// or the other way around (vice versa)
else if ((args.getCar().isNumber() && !args.getCdr().getCar().isNumber()) ||
(!args.getCar().isNumber() && args.getCdr().getCar().isNumber()))
{
return(BoolLit.getInstance(false));
}
// check if both number now...
else if (args.getCar().isNumber() && args.getCdr().getCar().isNumber())
{
// cast to new IntLits
IntLit intLit_1 = (IntLit)args.getCar();
IntLit intLit_2 = (IntLit)args.getCdr().getCar();
// check if the int values's are equal
if (intLit_1.getInt() == intLit_2.getInt())
{
// success: both same integer!
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
// first car is type boolean but second item is not boolean...
// or the other way around (vice versa)
else if ((args.getCar().isBool() && !args.getCdr().getCar().isBool()) ||
(!args.getCar().isBool() && args.getCdr().getCar().isBool()))
{
return(BoolLit.getInstance(false));
}
// check if both boolean now...
else if (args.getCar().isBool() && args.getCdr().getCar().isBool())
{
// cast nodes as new booleanNodes
BoolLit boolVal1 = (BoolLit)args.getCar();
BoolLit boolVal2 = (BoolLit)args.getCdr().getCar();
// check if the bool's equal
if (boolVal1.Equals(boolVal2))
{
// success: both same bool!
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
// first car is type builtIn but second item is not builtIn...
// or the other way around (vice versa)
else if ((args.getCar().isBuiltIn() && !args.getCdr().getCar().isBuiltIn()) ||
(!args.getCar().isBuiltIn() && args.getCdr().getCar().isBuiltIn()))
{
return(BoolLit.getInstance(false));
}
// check if both builtIn now...
else if (args.getCar().isBuiltIn() && args.getCdr().getCar().isBuiltIn())
{
// cast nodes as new builtIn
BuiltIn builtIn_val_1 = (BuiltIn)args.getCar();
BuiltIn builtIn_val_2 = (BuiltIn)args.getCdr().getCar();
// check if the builtIn's are identical
if (builtIn_val_1.getSymbol().Equals(builtIn_val_2.getSymbol()))
{
// success: both same builtIn!
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
// by process of elimination
//now
// a object that ends up tested here would be surely a closure...
// first car is type closure but second item is not closure...
// or the other way around (vice versa)
else if ((args.getCar().isProcedure() && !args.getCdr().getCar().isProcedure()) ||
(!args.getCar().isProcedure() && args.getCdr().getCar().isProcedure()))
{
return(BoolLit.getInstance(false));
}
// check if both closure now...
else if (args.getCar().isProcedure() && args.getCdr().getCar().isProcedure())
{
// cast nodes as new builtIn
Closure closure_val_1 = (Closure)args.getCar();
Closure closure_val_2 = (Closure)args.getCdr().getCar();
// check if the closure's are identical
if (closure_val_1.Equals(closure_val_2))
{
// success: both same closure!
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
// first car is type environment but second item is not environment...
// or the other way around (vice versa)
else if ((args.getCar().isEnvironment() && !args.getCdr().getCar().isEnvironment()) ||
(!args.getCar().isEnvironment() && args.getCdr().getCar().isEnvironment()))
{
return(BoolLit.getInstance(false));
}
// check if both environment now...
else if (args.getCar().isEnvironment() && args.getCdr().getCar().isEnvironment())
{
// cast nodes as new Environment
Environment environ_1 = (Environment)args.getCar();
Environment environ_2 = (Environment)args.getCdr().getCar();
// check if the environment's are identical
if (environ_1.Equals(environ_2))
{
// success: both same environment!
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
// first car is type String but second item is not String...
// or the other way around (vice versa)
else if ((args.getCar().isString() && !args.getCdr().getCar().isString()) ||
(!args.getCar().isString() && args.getCdr().getCar().isString()))
{
return(BoolLit.getInstance(false));
}
// check if both String now...
else if (args.getCar().isString() && args.getCdr().getCar().isString())
{
// cast nodes as new StringLits
StringLit String_1 = (StringLit)args.getCar();
StringLit String_2 = (StringLit)args.getCdr().getCar();
// check if the StringLit's are identical
if (String_1.getString().Equals(String_2.getString()))
{
// success: both same StringLit!
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
// eq? test note: there is one caveat. If the items are both quote terms... this will be handled directly in regular eval
// first car is type Pair but second item is not Pair...
// or the other way around (vice versa)
else if ((args.getCar().isPair() && !args.getCdr().getCar().isPair()) ||
(!args.getCar().isPair() && args.getCdr().getCar().isPair()))
{
return(BoolLit.getInstance(false));
}
// check if both are type Pair now...
else if (args.getCar().isPair() && args.getCdr().getCar().isPair())
{
// cast nodes as new cons Pair
Cons cons_1 = (Cons)args.getCar();
Cons cons_2 = (Cons)args.getCdr().getCar();
// check if the Cons's are identical
if (cons_1.Equals(cons_2))
{
// success: both same pair reference!
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
// illegal function for argument
}
else
{
Console.WriteLine("Error: Argument types for eq? cannot be recognized in context.");
return(Nil.getInstance());
}
}
else
{
Console.WriteLine("Error: null parameter _ or _ more than two arguments for eq? test is not permissable.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("car"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for car operation.");
return(Nil.getInstance());
}
// check if args first item given is a pair and check if the number of arguments given is correctly 1
if (args.getCar() != null && args.getCdr() != null && args.getCdr().isNull())
{
if (args.getCar().isPair())
{
if (args.getCar().getCar() != null)
{
return(args.getCar().getCar());
}
else
{
Console.WriteLine("Error: for car function_ , one of arguments to return is null.");
return(Nil.getInstance());
}
}
else
{
Console.WriteLine("Error: for car function_ , item given is not a pair.");
return(Nil.getInstance());
}
}
else
{
Console.WriteLine("Error: wrong number of arguments for car, tail is not nil. or element in arguments is null.");
return(Nil.getInstance());
}
}
else if (this.symbol.getName().Equals("cdr"))
{
// if there are no arguments, report error
if (args == null || args.isNull())
{
Console.WriteLine("Error: no arguments given for cdr operation.");
return(Nil.getInstance());
}
// check if args first item given is a pair and check if the number of arguments given is correctly 1
if (args.getCar() != null && args.getCar().isPair() && args.getCdr() != null && args.getCdr().isNull())
{
// check if argument's cdr is not null
if (args.getCar().getCdr() != null)
{
return(args.getCar().getCdr());
}
else
{
Console.WriteLine("Error: for cdr function_ , one of arguments to return is null.");
return(Nil.getInstance());
}
}
else
{
Console.WriteLine("Error: for cdr, item is not pair or wrong number of arguments for cdr: tail is not nil. or element in arguments is null.");
return(Nil.getInstance());
}
}
else
{
Console.WriteLine("Error: builtin is not identifiable.");
return(Nil.getInstance());
}
}
public void define(Node id, Node value)
{
Node a = new Cons(id, new Cons(value, Nil.getInstance()));
this.frame = new Cons(a, this.frame);
}
public override Node eval(Node cons_expression, Environment env1)
{
bool it_is_variable_Identifier__notFunction = false;
// check for null in construct of (define elem1 elem2)... and ends current method
// test1 checks if there might even be elements in expression
// test 2 checks if elem1 is a Identifier or not
// test 3 checks if elem2 exists
if (cons_expression.getCdr().isNull() || cons_expression.getCdr().getCar().isNull() ||
cons_expression.getCdr().getCdr().isNull())
{
return(new StringLit("Error: lacking items to be defined in (define ...) ."));
}
// the key of a frame is represented by the alist.getCar().getCar().getName();
// the val of a frame is represented by the alist.getCar().getCdr
// check if thing being defined is a function ... or just a variable
if (!cons_expression.getCdr().getCar().isPair())
{
it_is_variable_Identifier__notFunction = true;
}
else
{
it_is_variable_Identifier__notFunction = false;
}
if (it_is_variable_Identifier__notFunction)
{
if (cons_expression.getCdr().getCdr().getCar() == null)
{
return(new StringLit("Error: node with value in definition is null. cannot define."));
}
Node place_of_Node_with_Value = cons_expression.getCdr().getCdr().getCar();
if (place_of_Node_with_Value.isPair())
{
// assign val to id variable
// this in fact might assign our variable to point to a function term [indirectly.]
env1.define(cons_expression.getCdr().getCar(), place_of_Node_with_Value.eval(env1));
// finish here.
return(null);
}
else
{
if (place_of_Node_with_Value.isSymbol())
{
Node lookedUp_val_term = env1.lookup(place_of_Node_with_Value);
// error ... value to be assigned is undefined.
if (lookedUp_val_term == null)
{
return(new StringLit("Error: value to be assigned is undefined expression."));
}
else
{
// assign val looked up , unto id variable
// this in fact might assign our variable to point to a function term [indirectly.]
env1.define(cons_expression.getCdr().getCar(), lookedUp_val_term);
}
}
else
{
// assign val onto id variable
// this in fact might assign our variable to point to a function term [indirectly.]
env1.define(cons_expression.getCdr().getCar(), place_of_Node_with_Value);
}
// finish here.
return(null);
}
}
// work out storing function in environment
else
{
// "function assignment";
if (cons_expression.getCdr().getCar().getCdr().isNull() || cons_expression.getCdr().getCar().getCdr().isPair())
{
// normal case without dot in parameters of express
// create a lambda of this definition of a function
// lambda node = (cons 'lambda (cons (cdr (car (cdr a))) (cdr (cdr a))))
Node lambda_function = new Cons(new Ident("lambda"), new Cons(cons_expression.getCdr().getCar().getCdr(),
cons_expression.getCdr().getCdr()));
Closure defined_closure = new Closure(lambda_function, env1);
env1.define(cons_expression.getCdr().getCar().getCar(), defined_closure);
}
else
{
// particular spec case with a dot expression for parameters ... that ends the list without a nil
// create a lambda of this definition of a function
// lambda node = (cons 'lambda (cons (cdr (car (cdr a))) (cdr (cdr a))))
Node lambda_function = new Cons(new Ident("lambda"),
new Cons(
new Cons(cons_expression.getCdr().getCar().getCdr(), Nil.getInstance())
,
cons_expression.getCdr().getCdr()));
Closure defined_closure = new Closure(lambda_function, env1);
env1.define(cons_expression.getCdr().getCar().getCar(), defined_closure);
}
}
return(null);
}
private Node ConstructList(Hashtable dict)
{
Node values = new Node();
foreach (object kvp in dict)
{
values = new Cons(values, new Cons(new Ident((string) kvp), (Node)dict[kvp]));
}
return values;
}
public void define(Node id, Node val)
{
var newFrame = new Cons(id, new Cons(val, Nil.getInstance()));
frame = new Cons(newFrame, frame);
}
public void define(Node id, Node val)
{
Node definition = find(id, frame);
if (definition != null)
{
definition.setCar(val);
}
else
{
Node frame = new Cons(id, new Cons(val, Nil.getInstance()));
this.frame = new Cons(frame, this.frame);
}
}
public void define(Node id, Node val)
{
Node pair = new Cons(id, new Cons(val, Nil.getInstance()));
frame = new Cons(pair, frame);
}
// TODO: The method apply() should be defined in class Node
// to report an error. It should be overridden only in classes
// BuiltIn and Closure.
public override Node apply(Node args)
{
if (args == null)
{
return(null);
}
String name = symbol.getName();
Node car = args.getCar();
if (car == null || car.isNull())
{
car = Nil.getInstance();
}
Node cdr = args.getCdr();
if (cdr == null || cdr.isNull())
{
cdr = Nil.getInstance();
}
else
{
cdr = cdr.getCar();
}
if (name.equals("b+"))
{
if (car.isNumber() && cdr.isNumber())
{
return(new IntLit(car.getVal() + cdr.getVal()));
}
else
{
Console.Error.WriteLine("Invalid arguments for b+");
return(new StringLit(""));
}
}
else if (name.equals("b-"))
{
if (car.isNumber() && cdr.isNumber())
{
return(new IntLit(car.getVal() - cdr.getVal()));
}
else
{
Console.Error.WriteLine("Invalid arguments for b-");
return(new StringLit(""));
}
}
else if (name.equals("b*"))
{
if (car.isNumber() && cdr.isNumber())
{
return(new IntLit(car.getVal() * cdr.getVal()));
}
else
{
Console.Error.WriteLine("Invalid arguments for b*");
return(new StringLit(""));
}
}
else if (name.equals("b/"))
{
if (car.isNumber() && cdr.isNumber())
{
return(new IntLit(car.getVal() / cdr.getVal()));
}
else
{
Console.Error.WriteLine("Invalid arguments for b/");
return(new StringLit(""));
}
}
else if (name.equals("b="))
{
if (car.isNumber() && cdr.isNumber())
{
return(new BoolLit(car.getVal() == cdr.getVal()));
}
else
{
Console.Error.WriteLine("Invalid arguments for b=");
}
}
else if (name.equals("b>"))
{
if (car.isNumber() && cdr.isNumber())
{
return(new BoolLit(car.getVal() > cdr.getVal()));
}
else
{
Console.Error.WriteLine("Invalid arguments for b>");
}
}
else if (name.equals("b<"))
{
if (car.isNumber() && cdr.isNumber())
{
return(new BoolLit(car.getVal() < cdr.getVal()));
}
else
{
Console.Error.WriteLine("Invalid arguments for b<");
}
}
else if (name.equals("car"))
{
if (car.isNull())
{
return(car);
}
return(car.getCar());
}
else if (name.equals("cdr"))
{
if (car.isNull())
{
return(cdr);
}
return(cdr.getCdr());
}
else if (name.equals("cons"))
{
return(new Cons(car, cdr));
}
else if (name.equals("set-cdr!"))
{
car.setCdr(cdr);
return(car);
}
else if (name.equals("set-car!"))
{
car.setCar(cdr);
return(car);
}
else if (name.equals("symbol?"))
{
return(new BoolLit(car.isSymbol()));
}
else if (name.equals("number?"))
{
return(new BoolLit(car.isNumber()));
}
else if (name.equals("null?"))
{
return(new BoolLit(car.isNull()));
}
else if (name.equals("pair?"))
{
return(new BoolLit(car.isPair()));
}
else if (name.equals("eq?"))
{
if (car.isBoolean() && cdr.isBoolean())
{
return(new BoolLit(car.getBoolean() == cdr.getBoolean()));
}
else if (car.isNumber && cdr.isNumber())
{
return(new BoolLit(car.getVal() == cdr.getVal()));
}
else if (car.isString() && cdr.isString())
{
return(new BoolLit(car.getStringVal().equals(cdr.getStringVal())));
}
else if (car.isSymbol() && cdr.isSymbol)
{
return(new BoolLit(car.getName().equals(cdr.getName())));
}
else if (car.isNull() && cdr.isNull())
{
return(new BoolLit(true));
}
else if (car.isPair() && cdr.isPair())
{
Node opener = new Cons(car.getCar(), new Cons(cdr.getCar(), Nil.getInstance()));
Node closer = new Cons(car.getCdr(), new Cons(cdr.getCdr(), Nil.getInstance()));
return(new BoolLit(apply(opener).getBoolean() && apply(closer.getBoolean())));
}
return(new BoolLit(false));
}
else if (name.equals("procedure?"))
{
return(new BoolLit(car.isProcedure()));
}
else if (name.equals("display"))
{
return(car);
}
else if (name.equals("newline"))
{
return(new StringLit("", false));
}
else if (name.equals("exit") || name.equals("quit"))
{
return(0);
}
else if (name.equals("write"))
{
car.print(0);
return(new StringLit(""));
}
else if (name.equals("eval"))
{
return(car);
}
else if (name.equals("apply"))
{
return car.apply(cdr)
}
else if (name.equals("read"))
{
Parser isParsingMeOff = new Parser(new Scanner(Console.in));
return(isParsingMeOff.parseExp());
}
else
{
car.print(0);
return(Nil.getInstance());
}
return(new StringLit(">"));
}
private Node apply2(Node arg1, Node arg2)
{
string name = this.symbol.getName();
bool flag = name.Equals("eq?");
Node result;
if (flag)
{
bool flag2 = arg1.isSymbol() && arg2.isSymbol();
if (flag2)
{
string name2 = arg1.getName();
string name3 = arg2.getName();
result = BoolLit.getInstance(name2.Equals(name3));
}
else
{
result = BoolLit.getInstance(arg1 == arg2);
}
}
else
{
bool flag3 = name.Equals("cons");
if (flag3)
{
result = new Cons(arg1, arg2);
}
else
{
bool flag4 = name.Equals("set-car!");
if (flag4)
{
arg1.setCar(arg2);
result = Unspecific.getInstance();
}
else
{
bool flag5 = name.Equals("set-cdr!");
if (flag5)
{
arg1.setCdr(arg2);
result = Unspecific.getInstance();
}
else
{
bool flag6 = name.Equals("eval");
if (flag6)
{
bool flag7 = arg2.isEnvironment();
if (flag7)
{
result = arg1.eval((Environment)arg2);
}
else
{
Console.Error.WriteLine("Error: wrong type of argument");
result = Nil.getInstance();
}
}
else
{
bool flag8 = name.Equals("apply");
if (flag8)
{
result = arg1.apply(arg2);
}
else
{
bool flag9 = name[0] == 'b' && name.Length == 2;
if (flag9)
{
bool flag10 = arg1.isNumber() && arg2.isNumber();
if (flag10)
{
result = this.apply2(arg1.getIntVal(), arg2.getIntVal());
}
else
{
Console.Error.WriteLine("Error: invalid arguments");
result = Nil.getInstance();
}
}
else
{
Console.Error.WriteLine("Error: wrong number of arguments");
result = Nil.getInstance();
}
}
}
}
}
}
}
return result;
}
public override Node eval(Node node1, Environment env1)
{
// set up environment for scope of this let body
Environment current_env_of_let = new Environment(env1);
bool need_to_make_bindings = true;
// this will hold the list of evaluated arguments cumulatively.
// dummy value to start with
Cons evaluated_argsList__in_progress = new Cons(new IntLit(1), Nil.getInstance());
// check if there are items to assign to environment...
// and
// check if there is an body item for evaluation of let.
if (node1.getCdr() != null && node1.getCdr().isPair()
&& node1.getCdr().getCar() != null
&& node1.getCdr().getCdr() != null
&& node1.getCdr().getCdr().isPair())
{
// Make a list of values to be bound to keys given...
// __list_of_terms
Node current_lead_binding_node = node1.getCdr().getCar();
// this will hold the list of evaluated arguments cumulatively.
// Cons evaluated_argsList__in_progress;
// assign a dummy value
Cons current_fringe_of_argList = new Cons(new IntLit(1), Nil.getInstance());
bool has_more_bindings_in_list = true;
// this is the case that there are no items to be associated in Frame.
if (current_lead_binding_node.isNull() || !current_lead_binding_node.isPair())
{
has_more_bindings_in_list = false;
// now it is not necessary to bind anything
need_to_make_bindings = false;
}
bool first_run = true;
while (has_more_bindings_in_list)
{
if (current_lead_binding_node == null)
{
Console.WriteLine("Error: in Let, one of items in terms being bound has null lead node.");
return(Nil.getInstance());
}
//stopping criteria
if (current_lead_binding_node.isNull())
{
has_more_bindings_in_list = false;
break;
}
// get values if otherwise
if (current_lead_binding_node.isPair())
{
Node current_key_value_pair_item = current_lead_binding_node.getCar();
// check if this term is null or empty list
if (current_key_value_pair_item == null || current_key_value_pair_item.isNull())
{
Console.WriteLine("Error: in Let, one of key value pairs is either null or an empty list , nil.");
return(Nil.getInstance());
}
// check if this term is not a pair
if (!current_key_value_pair_item.isPair())
{
Console.WriteLine("Error: in Let, one of key value pairs is not a key value pair cons node.");
return(Nil.getInstance());
}
// get evaluated value here
Node node_to_add;
if (current_key_value_pair_item.getCdr() != null &&
!current_key_value_pair_item.getCdr().isNull() &&
current_key_value_pair_item.getCdr().isPair())
{
// first check if there is the right number of value, namely just one
if (current_key_value_pair_item.getCdr().getCdr() == null ||
!current_key_value_pair_item.getCdr().getCdr().isNull())
{
Console.WriteLine("Error: in let function call,... one of key value pairs has more than one value or a null for a tail.");
return(Nil.getInstance());
}
// check if item holding value is an expression that needs to be evaluated
if (current_key_value_pair_item.getCdr().getCar() != null &&
current_key_value_pair_item.getCdr().getCar().isPair())
{
// build new environment for this to be computed for.
Environment envExtend = new Environment(current_env_of_let);
node_to_add = current_key_value_pair_item.getCdr().getCar().eval(envExtend);
}
// lookup value from symbol in next case...
else if (current_key_value_pair_item.getCdr().getCar() != null &&
!current_key_value_pair_item.getCdr().getCar().isNull() &&
current_key_value_pair_item.getCdr().getCar().isSymbol())
{
node_to_add = current_env_of_let.lookup(current_key_value_pair_item.getCdr().getCar());
if (node_to_add == null)
{
Console.WriteLine("Error: one of values being bound in let is undefined in lookup, and thus null.");
return(Nil.getInstance());
}
// case where value is not an expression or a symbol, but only a literal
}
else if (current_key_value_pair_item.getCdr().getCar() != null)
{
node_to_add = current_key_value_pair_item.getCdr().getCar();
}
else
{
Console.WriteLine("Error: one of values being bound in let is null.");
return(Nil.getInstance());
}
}
else
{
Console.WriteLine("Error: in Let, one of items that should represent value, in a key value pair, is null or holds no value.");
return(Nil.getInstance());
}
// add latest value of key value pairs to cumulative list of values
if (first_run)
{
evaluated_argsList__in_progress = new Cons(node_to_add, Nil.getInstance());
current_fringe_of_argList = evaluated_argsList__in_progress;
first_run = false;
}
else
{
current_fringe_of_argList.setCdr(new Cons(node_to_add, Nil.getInstance()));
current_fringe_of_argList = (Cons)current_fringe_of_argList.getCdr();
}
// increment to next fringe key value pair item...
current_lead_binding_node = current_lead_binding_node.getCdr();
}
else
{
Console.WriteLine("Error: in Let, one of bindings does not have cons format.");
return(Nil.getInstance());
}
}
}
else
{
Console.WriteLine("Error: In let expression, ... either not enought arguments given , or null node encountered.");
return(Nil.getInstance());
}
if (need_to_make_bindings)
{
// bind each variable in key value pair
// current pair of all terms being binding
Node current_binding_node = node1.getCdr().getCar();
// current fring of value list
Node current_fringe_of_list_of_values = evaluated_argsList__in_progress;
// this will hold the list of evaluated arguments cumulatively.
//Cons evaluated_argsList__in_progress;
bool more_key_val_pairs_to_bind = true;
while (more_key_val_pairs_to_bind)
{
if (current_binding_node == null)
{
Console.WriteLine("Error: one of key value pairs lead node is null");
return(Nil.getInstance());
}
if (current_binding_node.isNull())
{
more_key_val_pairs_to_bind = false;
break;
}
if (current_binding_node.isPair())
{
if (current_binding_node.getCar() == null || current_binding_node.getCar().isNull())
{
Console.WriteLine("Error: in Let, one of key value pairs is either null or an empty list , nil.");
return(Nil.getInstance());
}
else if (!current_binding_node.getCar().isPair())
{
Console.WriteLine("Error: in Let, one of bindings does not have cons format.");
return(Nil.getInstance());
// go into binding association list
}
else if (current_binding_node.getCar().isPair())
{
if (current_binding_node.getCar().getCar() == null)
{
Console.WriteLine("Error: in Let, one of key/symbol fields is null.");
return(Nil.getInstance());
}
// check if this key is actually an identifier.
else if (current_binding_node.getCar().getCar().isSymbol())
{
current_env_of_let.define(current_binding_node.getCar().getCar(), current_fringe_of_list_of_values.getCar());
current_fringe_of_list_of_values = current_fringe_of_list_of_values.getCdr();
current_binding_node = current_binding_node.getCdr();
}
else
{
Console.WriteLine("Error: in Let, one of keys is not an identifier.");
return(Nil.getInstance());
}
}
}
else
{
Console.WriteLine("Error: in Let, pair field outer group does not have cons format.");
return(Nil.getInstance());
}
}
}
// jump ahead to body function expression of let.
Node current_locale_of_body = node1.getCdr().getCdr();
if (current_locale_of_body == null)
{
Console.WriteLine("Error: Let's body is Null");
return(Nil.getInstance());
}
// then check if the nil at list end without having anything fulfilled.
// also check to rule out there not being a child a cons node.
else if (current_locale_of_body.isNull() || !current_locale_of_body.isPair())
{
Console.WriteLine("Error: no arguments for evaluating in Begin statement .");
return(Nil.getInstance());
}
// start loop that flips through elements until we get at the last destination expression.
else
{
// initialize the item that may be returned.
Node returnItem;
// set a conditional and (on hold prospect) return element.
if (current_locale_of_body.getCar() == null)
{
Console.WriteLine("Error: one of expressions in begin's arguments null .");
return(Nil.getInstance());
}
else
{
returnItem = current_locale_of_body.getCar().eval(current_env_of_let);
}
bool hasAdditionalExp = false;
Node one_further_outExtending_tail = current_locale_of_body.getCdr();
// set one item extra in store of members of set of further tail items...
// if it is something to start a third part in a chain of further tail cycle.
// & nil term test
if (one_further_outExtending_tail != null && !one_further_outExtending_tail.isNull())
{
if (!one_further_outExtending_tail.isPair())
{
Console.WriteLine("Error: one of tail expressions is not in correct pair procession .");
return(Nil.getInstance());
}
else if (one_further_outExtending_tail.getCar() == null)
{
Console.WriteLine("Error: one of expressions in begin's arguments null .");
return(Nil.getInstance());
}
else
{
// set a conditional and (on hold prospect) return element.
returnItem = one_further_outExtending_tail.getCar().eval(current_env_of_let);
hasAdditionalExp = true;
}
}
// terminates with current return item. // because cant go further in chain for begin expression chain
else if (one_further_outExtending_tail != null && one_further_outExtending_tail.isNull())
{
hasAdditionalExp = false;
// end
return(returnItem);
}
else // ends here with error
{
Console.WriteLine("Error: Null encountered further on in Begin's expressions.");
return(Nil.getInstance());
}
// loops over each expression leading up to last.
while (hasAdditionalExp)
{
// set end now.
if (one_further_outExtending_tail.getCdr() != null && one_further_outExtending_tail.getCdr().isNull())
{
//end
hasAdditionalExp = false;
}
// go to next in sequence of cdr's
else if (one_further_outExtending_tail.getCdr() != null &&
!one_further_outExtending_tail.getCdr().isNull())
{
if (!one_further_outExtending_tail.getCdr().isPair())
{
Console.WriteLine("Error: one of expressions is not in correct pair procession .");
return(Nil.getInstance());
}
else if (one_further_outExtending_tail.getCdr().getCar() == null)
{
Console.WriteLine("Error: one of expressions in begin's arguments null .");
return(Nil.getInstance());
}
else
{
// set a conditional and (on hold prospect) return element.
returnItem = one_further_outExtending_tail.getCdr().getCar().eval(current_env_of_let);
hasAdditionalExp = true;
// increment to next in sequence of cdr's
one_further_outExtending_tail = one_further_outExtending_tail.getCdr();
}
}
else // ends here with error
{
Console.WriteLine("Error: Null encountered further on in Begin's expressions.");
return(Nil.getInstance());
}
} // while loop ended
return(returnItem);
}
}
