private Node evalArithmetic(int arg1, int arg2)
{
string name = symbol.getName();
if (name.Equals("b+"))
{
return(new IntLit(arg1 + arg2));
}
if (name.Equals("b-"))
{
return(new IntLit(arg1 - arg2));
}
if (name.Equals("b*"))
{
return(new IntLit(arg1 * arg2));
}
if (name.Equals("b/"))
{
return(new IntLit(arg1 / arg2));
}
if (name.Equals("b="))
{
return(BoolLit.getInstance(arg1 == arg2));
}
if (name.Equals("b<"))
{
return(BoolLit.getInstance(arg1 < arg2));
}
Console.Error.WriteLine("Error: unknown arithmetic symbol");
return(Nil.getInstance());
}
//syntax: if <test> <consequent> <alternate>
//syntax: if <test> <consequent>
public override Node eval(Node exp, Environment env)
{
var length = Node.length(exp);
if (length < 3 || length > 4)
{
Console.Error.WriteLine("Error: Invalid length for if expression");
return(Nil.getInstance());
}
var test = exp.getCdr().getCar();
var consequent = exp.getCdr().getCdr().getCar();
var alternate = new Node();
if (length == 4) //has alternates
{
alternate = exp.getCdr().getCdr().getCdr().getCar();
}
else //If <test> yields a false value and no <alternate> is specified, then the result of the expression is unspecified.
{
alternate = Unspecific.getInstance();
}
if (test.eval(env) != BoolLit.getInstance(false))
{
return(consequent.eval(env));
}
return(alternate.eval(env));
}
private Node BinArith(int arg1, int arg2, string s)
{
switch (s)
{
case "+":
return(new IntLit(arg1 + arg2));
case "-":
return(new IntLit(arg1 - arg2));
case "*":
return(new IntLit(arg1 * arg2));
case "/":
return(new IntLit(arg1 / arg2));
case "=":
return(BoolLit.getInstance(arg1 == arg2));
case "<":
return(BoolLit.getInstance(arg1 < arg2));
case ">":
return(BoolLit.getInstance(arg1 > arg2));
default:
return(null);
}
}
// to evaluate expressions of the form '(if b t e)',
// evaluate b, then if b is not the boolean constant #f,
// evaluate t and return the result. otherwise, evaluate
// e and return the result.
public override Node eval(Node t, Environment env)
{
// if cdr is nil, return nil (error state)
if (t.getCdr() == Nil.getInstance())
{
Console.Error.WriteLine("Special form 'If' evaluated with no arguments");
return(Nil.getInstance());
}
// get cdr of expression (conditional and execution statements)
t = t.getCdr();
// if cdr of t is nil, expression has a conditional but no executable statements (error state)
if (t.getCdr() == Nil.getInstance())
{
Console.Error.WriteLine("Special form 'If' evaluated with insufficient arguments");
return(Nil.getInstance());
}
// evaluate car of b (conditional). if b is not #f, evaluate and return t.
if (t.getCar().eval(env) != BoolLit.getInstance(false))
{
return(t.getCdr().getCar().eval(env));
}
else
{
// otherwise, b is #f. evaluate and return e.
// if e is nil, statement is still valid. interpreter will parse and return nil.
return(t.getCdr().getCdr().getCar().eval(env));
}
}
public Boolean checkTrue(Node cond, Environment e)
{
Node check = cond.eval(cond, e);
if (check.isBool() == true)
{
BoolLit boolVal = (BoolLit)check;
return(boolVal.getVal());
}
return(true);
}
private Node apply2(Node arg1, Node arg2)
{
string name = symbol.getName();
if (name.Equals("eq?"))
{
if (arg1.isSymbol() && arg2.isSymbol())
{
return(BoolLit.getInstance(arg1.getName().Equals(arg2.getName())));
}
return(BoolLit.getInstance(arg1 == arg2));
}
if (name.Equals("cons"))
{
return(new Cons(arg1, arg2));
}
if (name.Equals("set-car!"))
{
arg1.setCar(arg2);
return(Unspecific.getInstance());
}
if (name.Equals("set-cdr!"))
{
arg1.setCdr(arg2);
return(Unspecific.getInstance());
}
if (name.Equals("eval"))
{
if (arg2.isEnvironment())
{
Environment envArg1 = (Environment)arg1;
return(arg1.eval(envArg1));
}
Console.Error.WriteLine("Error: argument is not an environment");
return(Nil.getInstance());
}
if (name.Equals("apply"))
{
return(arg1.apply(arg2));
}
if (name[0].Equals('b') && name.Length == 2)
{
if (arg1.isNumber() && arg2.isNumber())
{
return(evalArithmetic(arg1.getIntVal(), arg2.getIntVal()));
}
Console.Error.WriteLine("Error: invalid arguments");
return(Nil.getInstance());
}
Console.Error.WriteLine("Error: wrong number of arguments");
return(Nil.getInstance());
}
private Node evalClauses(Node exp, Environment env)
{
if (exp.isNull())
{
return(Unspecific.getInstance());
}
var clause = exp.getCar();
if (Node.length(clause) <= 0)
{
Console.Error.WriteLine("Error: invalid cond expression");
return(Nil.getInstance());
}
var testExp = clause.getCar();
var expression = clause.getCdr();
if (testExp.isSymbol() && testExp.getName().Equals("else"))
{
if (!expression.isNull() && exp.getCdr().isNull())
{
return(evalExp(expression, env));
}
Console.Error.WriteLine("Error: invalid expression");
return((Node)Nil.getInstance());
}
var testValid = testExp.eval(env);
if (testValid == BoolLit.getInstance(false))
{
var nextExps = exp.getCdr();
return(evalClauses(nextExps, env));
}
if (expression.isNull())
{
return(BoolLit.getInstance(true));
}
var exp1 = expression.getCar();
if (!exp1.isSymbol() || !exp1.getName().Equals("=>"))
{
return(evalExp(expression, env));
}
if (Node.length(expression) != 2)
{
Console.Error.WriteLine("Error: invalid cond expression");
return(Nil.getInstance());
}
var cdr = expression.getCdr().getCar();
return(cdr.eval(env).apply(BoolLit.getInstance(true)));
}
public override Node eval(Node t, Environment env)
{
Node test = t.getCdr().getCar();
Node consq = t.getCdr().getCdr();
Node alt = consq.getCdr();
if (test.eval(env) == BoolLit.getInstance(true))
{
return(consq.getCar().eval(env));
}
else if (!(alt is Nil))
{
return(alt.getCar().eval(env));
}
Console.Error.WriteLine("Error: If not properly formatted");
return(Nil.getInstance());
}
private Node apply1(Node arg1)
{
string name = symbol.getName();
if (name.Equals("car"))
{
return(arg1.getCar());
}
if (name.Equals("cdr"))
{
return(arg1.getCdr());
}
if (name.Equals("number?"))
{
return(BoolLit.getInstance(arg1.isNumber()));
}
if (name.Equals("symbol?"))
{
return(BoolLit.getInstance(arg1.isSymbol()));
}
if (name.Equals("null?"))
{
return(BoolLit.getInstance(arg1.isNull()));
}
if (name.Equals("pair?"))
{
return(BoolLit.getInstance(arg1.isPair()));
}
if (name.Equals("procedure?"))
{
return(BoolLit.getInstance(arg1.isProcedure()));
}
if (name.Equals("write"))
{
arg1.print(-1);
return(Unspecific.getInstance());
}
if (name.Equals("display"))
{
Console.Write(arg1);
return(Unspecific.getInstance());
}
Console.Error.WriteLine("Error: wrong number of arguments");
return(Nil.getInstance());
}
public override Node eval(Node t, Environment env)
{
while (!(t.getCdr() is Nil))
{
t = t.getCdr();
if (!(t.getCar() is Cons))
{
Console.Error.WriteLine("Error: unexpected argument");
}
Node n = t.getCar().getCar().eval(env);
if (t.getCar().getCar().eval(env).Equals(BoolLit.getInstance(true)))
{
t = t.getCar();
return(t.getCdr().getCar().eval(env));
}
}
// get else to work...?
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();
}
Node cnd;
Node thn;
Node els;
if (numArgs < 2 || numArgs > 3)
{
Console.Error.WriteLine("Error: invalid expression");
return(Nil.getInstance());
}
else
{
cnd = exp.getCdr().getCar();
thn = exp.getCdr().getCdr().getCar();
if (numArgs == 3)
{
els = exp.getCdr().getCdr().getCdr().getCar();
}
else
{
els = new StringLit("#{Unspecific}", false);
}
}
if (cnd.eval(env) != BoolLit.getInstance(false))
{
return(thn.eval(env));
}
return(els.eval(env));
}
public override Node eval(Environment env, Node args)
{
Node result = BoolLit.getInstance(false), test, cases = args;
// Iterate through each case test until it evaluates to true or we hit the end
do
{
cases = cases.getCdr();
test = cases.getCar().getCar();
if (test.getName() == "else")
{
break;
}
result = test.eval(env);
} while (cases.getCdr().isNull() == false && result == BoolLit.getInstance(false));
// if a expr value returned true or we hit an else clause
if (result != BoolLit.getInstance(false) || test.getName() == "else")
{
// If there was a test with no other expressions, apply the test
if (cases.getCar().getCdr().isNull() == true)
{
return(args.getCar().eval(env).apply(result));
}
// Otherwise apply the following expressions
else
{
Node debug = cases.getCar().getCdr(), debug2 = args.getCar();
return(args.getCar().eval(env).apply(cases.getCar().getCdr().eval(env)));
}
}
else
{
return(new StringLit("#unspecified"));
}
}
// DONE :: 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)
{
string name = symbol.getName();
int numArgs = 0;
Node arg1;
Node arg2;
Node tempArgs = args;
while (!tempArgs.isNull())
{
numArgs++;
tempArgs = tempArgs.getCdr();
}
if (numArgs == 0)
{
if (name.Equals("read"))
{
Parser parser = new Parser(new Scanner(Console.In), new TreeBuilder());
Node exp = (Node)parser.parseExp();
if (!exp.isNull())
{
return(exp);
}
return(new StringLit("End of file", false));
}
else if (name.Equals("newline"))
{
Console.WriteLine();
return(new StringLit("#{Unspecific}", false));
}
else if (name.Equals("interaction-environment"))
{
return(Scheme4101.env);
}
Console.Error.WriteLine("Error: invalid input");
return(Nil.getInstance());
}
else if (numArgs == 1)
{
arg1 = args.getCar();
if (name.Equals("symbol?"))
{
return(BoolLit.getInstance(arg1.isSymbol()));
}
if (name.Equals("number?"))
{
return(BoolLit.getInstance(arg1.isNumber()));
}
if (name.Equals("car"))
{
return(arg1.getCar());
}
if (name.Equals("cdr"))
{
return(arg1.getCdr());
}
if (name.Equals("null?"))
{
return(BoolLit.getInstance(arg1.isNull()));
}
if (name.Equals("pair?"))
{
return(BoolLit.getInstance(arg1.isPair()));
}
if (name.Equals("procedure?"))
{
return(BoolLit.getInstance(arg1.isProcedure()));
}
if (name.Equals("write"))
{
arg1.print(0);
return(new StringLit("#{Unspecific}", false));
}
if (name.Equals("display"))
{
StringLit.printQuotes = false;
arg1.print(0);
StringLit.printQuotes = true;
return(new StringLit("#{Unspecific}", false));
}
Console.Error.WriteLine("Error: invalid input");
return(Nil.getInstance());
}
else if (numArgs == 2)
{
arg1 = args.getCar();
arg2 = args.getCdr().getCar();
if (name.Equals("eq?"))
{
if (arg1.isSymbol() && arg2.isSymbol())
{
return(BoolLit.getInstance(arg1.getName().Equals(arg2.getName())));
}
return(BoolLit.getInstance(arg1 == arg2));
}
if (name.Equals("cons"))
{
return(new Cons(arg1, arg2));
}
if (name.Equals("set-car!"))
{
arg1.setCar(arg2);
return(new StringLit("#{Unspecific}", false));
}
if (name.Equals("set-cdr!"))
{
arg1.setCdr(arg2);
return(new StringLit("#{Unspecific}", false));
}
if (name.Equals("eval"))
{
return(arg1.eval((Environment)arg2));
}
if (name.Equals("apply"))
{
return(arg1.apply(arg2));
}
int int1;
int int2;
if (arg1.isNumber() && arg2.isNumber())
{
int1 = arg1.getValue();
int2 = arg2.getValue();
}
else
{
Console.Error.WriteLine("Error: invalid argument types");
return(Nil.getInstance());
}
if (name.Equals("b+"))
{
if (arg1.isNumber() && arg2.isNumber())
{
return(new IntLit(int1 + int2));
}
}
if (name.Equals("b-"))
{
return(new IntLit(int1 - int2));
}
if (name.Equals("b*"))
{
return(new IntLit(int1 * int2));
}
if (name.Equals("b/"))
{
return(new IntLit(int1 / int2));
}
if (name.Equals("b="))
{
return(BoolLit.getInstance(int1 == int2));
}
if (name.Equals("b<"))
{
return(BoolLit.getInstance(int1 < int2));
}
Console.Error.WriteLine("Error: invalid function");
return(Nil.getInstance());
}
else
{
Console.Error.WriteLine("Error: wrong number of args");
return(Nil.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)
{
Node result = null;
int numArgs = numArguments(args);
switch (symbol.getName())
{
case "begin":
// The value(s) of the last expression is(are) returned
while (args.getCdr().isNull() == false)
{
args = args.getCdr();
}
return(args.getCar());
case "cond":
// The value(s) of the last expression is(are) returned
while (args.getCdr().isNull() == false)
{
args = args.getCdr();
}
return(args.getCar());
case "if":
if (args.getCar() == BoolLit.getInstance(true))
{
return(args.getCdr().getCar());
}
else if (args.getCdr().getCdr().isPair())
{
return(args.getCdr().getCdr().getCar());
}
else
{
return(new StringLit("#unspecified"));
}
case "let":
// The value(s) of the last expression is(are) returned
while (args.getCdr().isNull() == false)
{
args = args.getCdr();
}
return(args.getCar());
case "quote":
return(args.getCdr().getCar());
case "read":
return((Node)args.parser.parseExp());
case "write":
args.print(0);
// Not sure what Node to return here. Probably just return the blank Node
break;
case "symbol?":
// symbol? only accepts 1 argument
if (numArgs != 1)
{
return(new StringLit("Error: wrong number of arguments for 'symbol?'"));
}
else
{
if (args.getCar().isSymbol())
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
case "number?":
// number? only accepts 1 argument
if (numArgs != 1)
{
return(new StringLit("Error: wrong number of arguments for 'number?'"));
}
else
{
if (args.getCar().isNumber())
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
}
case "car":
if (args.isPair() == false)
{
return(new StringLit("Error: Argument to 'car' is not a pair."));
}
else
{
return(args.getCar());
}
case "cdr":
if (args.isPair() == false)
{
return(new StringLit("Error: Argument to 'cdr' is not a pair."));
}
else
{
return(args.getCdr());
}
case "cons":
// make sure only two arguments are provided
if (args.getCdr().isPair() != true && args.getCdr().getCdr().isNull() == false)
{
return(new StringLit("Error: Function 'cons' requires two arguments."));
}
else
{
return(args);
}
case "set-car!":
// make sure only a list and value are provided
if (args.getCar().isPair() == false || args.getCdr().getCar().isPair() == true || args.getCdr().getCdr().isNull() == false)
{
return(new StringLit("Error: Function 'set-car!' requires a list and value"));
}
else
{
args.getCar().setCar(args.getCdr().getCar());
return(new StringLit("no values returned;"));
}
case "set-cdr!":
// make sure only a list and value are provided
if (args.getCar().isPair() == false || args.getCdr().getCar().isPair() == true || args.getCdr().getCdr().isNull() == false)
{
return(new StringLit("Error: Function 'set-cdr!' requires a list and value"));
}
else
{
args.getCar().setCdr(args.getCdr().getCar());
return(new StringLit("no values returned;"));
}
case "null?":
if (args.getCar().isNull() == true)
{
return(BoolLit.getInstance(true));
}
// null? only accepts one argument
else if (args.getCdr().isPair() == true)
{
return(new StringLit("Error: 'null?' only accept one argument."));
}
else
{
return(BoolLit.getInstance(false));
}
case "pair?":
// pair? only accept one argument
if (args.getCdr().isPair() == true)
{
return(new StringLit("Error: 'pair?' only accepts one argument."));
}
else if (args.getCar().isPair())
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
case "eq?":
// eq? only accepts two arguments
if (args.getCdr().getCdr().isNull() == false)
{
return(new StringLit("Error: 'eq?' only accepts one argument"));
}
else if (args.getCar() == args.getCdr().getCar()) // Not sure if this is going to work, actually
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
case "procedure?":
//procedure only accepts 1 argument (I think)
if (args.getCdr().isNull() == false)
{
return(new StringLit("Error: 'procedure?' only accepts one argument"));
}
else if (args.getCar().isProcedure() == true)
{
return(BoolLit.getInstance(true));
}
else
{
return(BoolLit.getInstance(false));
}
default:
break;
}
// Now we check for the binary arithmetic builtins
IntLit num1 = new IntLit(0), num2;
if (symbol.getName() == "b/") // The division function has 1 as the default value instead of 0 when only 1 argument is provided
{
num1 = new IntLit(1);
}
// If the arguments aren't numerical, the IntLit casts will fail and the catch block executes.
// If there are 0 arguments the first cast will fail, and if there are more than 2 an Exception is thrown
try
{
num2 = (IntLit)args.getCar();
// Check for a second argument
if (args.getCdr().isPair() == true)
{
// We do this swap because if we have only 1 argument, we're doing 0 - num2. If we have 2, we're doing num1-num2.
num1 = num2;
num2 = (IntLit)args.getCdr().getCar();
if (args.getCdr().getCdr().isNull() == false)
{
throw new Exception();
}
}
else if (symbol.getName() == "b=" || symbol.getName() == "b<")
{
return(result = new StringLit("Error: binary arithmetic operation '" + symbol.getName() + "' expects two numerical 2 arguments."));
}
}
catch
{
return(result = new StringLit("Error: binary arithmetic operations expect 1 or 2 numerical arguments."));
}
if (symbol.getName() == "b+")
{
result = new IntLit(num1.getInt() + num2.getInt());
}
else if (symbol.getName() == "b-")
{
result = new IntLit(num1.getInt() - num2.getInt());
}
else if (symbol.getName() == "b*")
{
result = new IntLit(num1.getInt() * num2.getInt());
}
else if (symbol.getName() == "b/")
{
if (num2.getInt() == 0)
{
return(result = new StringLit("Error: Dividing by 0."));
}
result = new IntLit(num1.getInt() / num2.getInt());
}
else if (symbol.getName() == "b=")
{
if (num1.getInt() == num2.getInt())
{
result = BoolLit.getInstance(true);
}
else
{
result = BoolLit.getInstance(false);
}
}
else if (symbol.getName() == "b<")
{
if (num1.getInt() < num2.getInt())
{
result = BoolLit.getInstance(true);
}
else
{
result = BoolLit.getInstance(false);
}
}
return(result);
}
public override Node eval(Environment env, Node args = null)
{
return(BoolLit.getInstance(boolVal));
}
public static BoolLit getTrue()
{
if(trueLit == null)
trueLit = new BoolLit(true);
return trueLit;
}
public static BoolLit getFalse()
{
if (falseLit == null)
falseLit = new BoolLit(false);
return falseLit;
}
public INode buildBoolLit(bool b)
{
return(BoolLit.getInstance(b));
}
// 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());
}
}
// TODO: The method apply() should be defined in class Node
// to report an error. It should be overridden only in classes
// BuiltIn and Closure. Probably will have to include calls to eval
public override Node apply(Node args)
{
if (args == null)
{
return(null);
}
String Symbol = symbol.getName();
Node arg1 = args.getCar(), arg2 = args.getCdr().getCar();
switch (Symbol)
{
case "symbol?":
return(BoolLit.getInstance(arg1.isSymbol()));
case "number?":
return(BoolLit.getInstance(arg1.isNumber()));
case "b+":
return(BinArith(((IntLit)arg1).getValue(), ((IntLit)arg2).getValue(), "+"));
case "b-":
return(BinArith(((IntLit)arg1).getValue(), ((IntLit)arg2).getValue(), "-"));
case "b*":
return(BinArith(((IntLit)arg1).getValue(), ((IntLit)arg2).getValue(), "*"));
case "b/":
return(BinArith(((IntLit)arg1).getValue(), ((IntLit)arg2).getValue(), "/"));
case "b=":
return(BinArith(((IntLit)arg1).getValue(), ((IntLit)arg2).getValue(), "="));
case "b>":
return(BinArith(((IntLit)arg1).getValue(), ((IntLit)arg2).getValue(), ">"));
case "b<":
return(BinArith(((IntLit)arg1).getValue(), ((IntLit)arg2).getValue(), "<"));
case "car":
if (arg1.isNull())
{
return(arg1); //arg1==nil or null?
}
else
{
return(arg1.getCar());
}
case "cdr": // ????????????????
if (arg1.isNull())
{
return(arg1); //arg1==nil or null?
}
else
{
return(arg1.getCdr());
}
case "cons":
return(new Cons(arg1, arg2));
case "set-car!":
arg1.setCar(arg2);
return(arg1);
case "set-cdr!":
arg1.setCdr(arg2);
return(arg1);
case "null?":
return(BoolLit.getInstance(arg1.isNull()));
case "pair?":
return(BoolLit.getInstance(arg1.isPair()));
case "eq?":
return(BoolLit.getInstance(arg1 == arg2));
case "procedure?":
return(BoolLit.getInstance(arg1.isProcedure()));
case "read": //call parser and returns parse tree
Parser parse = new Parser(new Scanner(Console.In), new TreeBuilder());
return((Node)parse.parseExp());
case "write":
return(new StringLit("Cha{" + arg1.ToString() + "/*WRITE*\\}"));
case "display":
return(new StringLit("Cha{" + arg1.ToString() + "/*DISPLAY*\\}")); //not truly implemented, placeholder code I tink
case "newline": //\n?
return(new StringLit("\n"));
case "eval":
return(arg1.eval(new Environment()));
case "apply":
return(arg1.apply(arg2));
case "interaction-environment":
//args.env
//do
//{
// //TODO
// env = new Environment();
//} while (env != null);
return(new Environment());
}
return(null);
}
// check if null/end of last clause:
// return unspecific
// check if else clause:
// yes: eval exps and return value of last exp
// check if clause has exp
// if no exp: return value of test
// if test failed: go to next clause
// check alt or normal form
// eval expression(s) appropriately
private Node evalConds(Node clauses, Environment env)
{
// if end of clauses and nothing has been returned, return unspecific
if (clauses.isNull())
{
return(new StringLit("#{Unspecific}", false));
}
Node cnd = clauses.getCar();
// make sure clause isnt empty
if (cnd.isNull())
{
Console.Error.WriteLine("Error: invalid expression");
return(Nil.getInstance());
}
Node test = cnd.getCar();
Node exprs = cnd.getCdr();
Node expr;
if (test.isSymbol() && test.getName().Equals("else"))
{
//erorr if no expression or else is not last clause
if (exprs.isNull() || !clauses.getCdr().isNull())
{
Console.Error.WriteLine("Error: invalid expression");
return(Nil.getInstance());
}
else
{
// evaluate each expr in exprs then return the last one
Node car = Nil.getInstance();
while (!exprs.isNull())
{
expr = exprs.getCar();
car = expr.eval(env);
if (expr.isPair())
{
Node cdr = expr.getCdr();
while (!cdr.isNull())
{
car = cdr.getCar().eval(env);
cdr = cdr.getCdr();
}
}
exprs = exprs.getCdr();
}
return(car);
}
}
Node testEval = test.eval(env);
// if clause is a test with no expressions
if (exprs.isNull())
{
return(testEval);
}
// if test failed go to next clause
if (testEval == BoolLit.getInstance(false))
{
return(evalConds(clauses.getCdr(), env));
}
// if alternate form
if (exprs.getCar().getName().Equals("=>"))
{
return(exprs.getCdr().getCar().eval(env).apply(testEval));
}
//normal form: iterate exprs, evaluate each expr, then return last expr
else
{
Node car = Nil.getInstance();
while (!exprs.isNull())
{
expr = exprs.getCar();
car = expr.eval(env);
if (expr.isPair())
{
Node cdr = expr.getCdr();
while (!cdr.isNull())
{
car = cdr.getCar().eval(env);
cdr = cdr.getCdr();
}
}
exprs = exprs.getCdr();
}
return(car);
}
}
// to evaluate expressions of the form '(cond (b1 ...) ... (bn ...))',
// evaluate b1 through bn until a condition not equal to #f is found.
// if this case is of the form '(bi)', return bi.
// if this case is of the form '(bi e1 ... en)', evaluate e1-en and return
// the result of evaluating en
public override Node eval(Node t, Environment env)
{
// if cond expression has no cdr, invalid syntax (error state)
if (t.getCdr() == Nil.getInstance())
{
Console.Error.WriteLine("Special form 'cond' evaluated with no arguments");
return(Nil.getInstance());
}
// get cdr of expression
t = t.getCdr();
// while cond statement has a cdr and its car (bi) evaluates to #f, keep moving down the tree
while (t.getCdr() != Nil.getInstance() && t.getCar().getCar().eval(env) == BoolLit.getInstance(false))
{
t = t.getCdr();
}
// once a condition is found that is not #f or end of statement,
// get car of t to evaluate
t = t.getCar();
// if cdr of t is null, statement is of form '(bi)', so return bi
if (t.getCdr().eval(env) == Nil.getInstance())
{
return(t.getCar());
}
// otherwise, statement is of form (bi e1 ... en)
// evaluate e1 through en, then return the result of evaluating en
// first evaluate e1 through e(n-1)
while (t.getCdr() != Nil.getInstance())
{
t.getCdr().getCar().eval(env);
t = t.getCdr();
}
// finally evaluate and return en
return(t.getCar().eval(env));
}
public override Node apply(Node args)
{
//set initial values
string argsName = symbol.getName();
int argsAmount = 0;
//initialize
Node firstArgs = null;
bool b1 = false;
Node secondArgs = null;
bool b2 = false;
//setup initial Args
while (!args.isNull())
{
argsAmount = argsAmount + 1;
if (argsAmount == 1)
{
firstArgs = args.getCar();
b1 = true;
}
if (argsAmount == 2)
{
secondArgs = args.getCar();
b2 = true;
}
args = args.getCdr();
}
//start apply based on amount or arguements and type of arguement
//switch statement possibly
if (argsAmount == 0)
{
// read
if (argsName.Equals("read"))
{
Scanner s = new Scanner(Console.In);
TreeBuilder tb = new TreeBuilder();
Parser p = new Parser(s, tb);
Node n = (Node)p.parseExp();
if (n != null)
{
return(n);
}
}
//newline
else if (argsName.Equals("newline"))
{
Console.WriteLine();
//check value upspecified
return(new StringLit(" "));
}
//i-e
else if (argsName.Equals("interaction-environment"))
{
return(Scheme4101.env);
}
//invalid argsName given
else
{
Console.Error.WriteLine("invalid arguemtent name given");
return(Nil.getInstance());
}
}
else if (argsAmount == 1)
{
//symbol?
if (argsName.Equals("symbol?"))
{
bool b = firstArgs.isSymbol();
return(BoolLit.getInstance(b));
}
//number?
else if (argsName.Equals("number?"))
{
bool b = firstArgs.isNumber();
return(BoolLit.getInstance(b));
}
//car
else if (argsName.Equals("car"))
{
return(firstArgs.getCar());
}
//cdr
else if (argsName.Equals("cdr"))
{
return(firstArgs.getCdr());
}
//null?
//b1?
else if (argsName.Equals("null?") && b1)
{
bool b = firstArgs.isNull();
return(BoolLit.getInstance(b));
}
//pair
else if (argsName.Equals("pair?"))
{
bool b = firstArgs.isPair();
return(BoolLit.getInstance(b));
}
//precedure
else if (argsName.Equals("procedure?"))
{
bool b = firstArgs.isProcedure();
return(BoolLit.getInstance(b));
}
//write
else if (argsName.Equals("write"))
{
firstArgs.print(0);
//return value unspecified
return(new StringLit(" "));
}
//display
else if (argsName.Equals("display"))
{
//temp change value
StringLit.quoted = false;
firstArgs.print(0);
//reset changed value
StringLit.quoted = true;
//return value unspecified
return(new StringLit(" "));
}
}
else if (argsAmount == 2)
{
//eq?
if (argsName.Equals("eq?"))
{
bool bt1 = firstArgs.isSymbol();
bool bt2 = secondArgs.isSymbol();
if (bt1 && bt2)
{
bool bt3 = firstArgs.getName().Equals(secondArgs.getName());
return(BoolLit.getInstance(bt3));
}
else
{
bool bt4 = firstArgs == secondArgs;
return(BoolLit.getInstance(bt4));
}
}
//cons
else if (argsName.Equals("cons"))
{
return(new Cons(firstArgs, secondArgs));
}
//set-car!
else if (argsName.Equals("set-car!"))
{
firstArgs.setCar(secondArgs);
//return value unspecified
return(new StringLit(" "));
}
//set-cdr!
else if (argsName.Equals("set-cdr!"))
{
firstArgs.setCdr(secondArgs);
//return value unspecified
return(new StringLit(" "));
}
//eval
else if (argsName.Equals("eval"))
{
return(firstArgs.eval((Environment)secondArgs));
}
//apply
else if (argsName.Equals("apply"))
{
return(firstArgs.apply(secondArgs));
}
else
{
return(Nil.getInstance());
}
//binary arithematic opecations tmp vars
int bo1 = 0;
int bo2 = 0;
if (firstArgs.isNumber())
{
bo1 = firstArgs.getValue();
}
else if (secondArgs.isNumber())
{
bo2 = secondArgs.getValue();
}
else
{
Console.Error.WriteLine("invalid arguemtent name given");
return(Nil.getInstance());
}
//b+
if (argsName.Equals("b+"))
{
return(new IntLit(bo1 + bo2));
}
//b-
else if (argsName.Equals("b-"))
{
return(new IntLit(bo1 - bo2));
}
//b*
else if (argsName.Equals("b*"))
{
return(new IntLit(bo1 * bo2));
}
//b/
else if (argsName.Equals("b/"))
{
return(new IntLit(bo1 / bo2));
}
//b=
else if (argsName.Equals("b="))
{
bool b = bo1 == bo2;
return(BoolLit.getInstance(b));
}
//b<
else if (argsName.Equals("b<"))
{
bool b = bo1 < bo2;
return(BoolLit.getInstance(b));
}
else
{
Console.Error.WriteLine("Aritheatic Operation Error");
return(Nil.getInstance());
}
}
//invalid argsName given
else
{
Console.Error.WriteLine("invalid arguemtent name given");
return(Nil.getInstance());
}
return(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)
{
// return new StringLit("Error: BuiltIn.apply not yet implemented");
Node arg1 = Nil.getInstance();
String symName = symbol.getName();
if (symName.Equals("interaction-environment"))
{
return(global);
}
if (symName.Equals("newline"))
{
Console.WriteLine();
return(Void.getInstance());
}
if (!(args.getCar() is Nil))
{
arg1 = args.getCar();
}
Node arg2 = Nil.getInstance();
if (!args.getCdr().isNull())
{
arg2 = args.getCdr().getCar();
}
if (symName.Equals("symbol?"))
{
return(BoolLit.getInstance(arg1.isSymbol()));
}
if (symName.Equals("number?"))
{
return(BoolLit.getInstance(arg1.isNumber()));
}
if (symName.Equals("b+"))
{
if (arg1.isNumber() & arg2.isNumber())
{
return(new IntLit(arg1.getVal() + arg2.getVal()));
}
}
if (symName.Equals("b-"))
{
if (arg1.isNumber() & arg2.isNumber())
{
return(new IntLit(arg1.getVal() - arg2.getVal()));
}
}
if (symName.Equals("b*"))
{
if (arg1.isNumber() & arg2.isNumber())
{
return(new IntLit(arg1.getVal() * arg2.getVal()));
}
}
if (symName.Equals("b/"))
{
if (arg1.isNumber() & arg2.isNumber())
{
return(new IntLit(arg1.getVal() / arg2.getVal()));
}
}
if (symName.Equals("b="))
{
if (arg1.isNumber() & arg2.isNumber())
{
return(BoolLit.getInstance(arg1.getVal() == arg2.getVal()));
}
}
if (symName.Equals("b<"))
{
if (arg1.isNumber() & arg2.isNumber())
{
return(BoolLit.getInstance(arg1.getVal() < arg2.getVal()));
}
}
if (symName.Equals("b>"))
{
if (arg1.isNumber() & arg2.isNumber())
{
return(BoolLit.getInstance(arg1.getVal() > arg2.getVal()));
}
}
if (symName.Equals("b>="))
{
if (arg1.isNumber() & arg2.isNumber())
{
return(BoolLit.getInstance(arg1.getVal() >= arg2.getVal()));
}
}
if (symName.Equals("b<="))
{
if (arg1.isNumber() & arg2.isNumber())
{
return(BoolLit.getInstance(arg1.getVal() <= arg2.getVal()));
}
}
if (symName.Equals("car"))
{
return(arg1.getCar());
}
if (symName.Equals("cdr"))
{
return(arg1.getCdr());
}
if (symName.Equals("set-car!"))
{
arg1.setCar(arg2);
return(Void.getInstance());
}
if (symName.Equals("set-cdr!"))
{
arg1.setCdr(arg2);
return(Void.getInstance());
}
if (symName.Equals("null?"))
{
return(BoolLit.getInstance(arg1.isNull()));
}
if (symName.Equals("pair?"))
{
return(BoolLit.getInstance(arg1.isPair()));
}
if (symName.Equals("eq?"))
{
if (arg1.isSymbol() && arg2.isSymbol())
{
return(BoolLit.getInstance(arg1.getName().Equals(arg2.getName())));
}
return(BoolLit.getInstance(arg1 == arg2));
}
if (symName.Equals("procedure?"))
{
return(BoolLit.getInstance(arg1.isProcedure()));
}
if (symName.Equals("read"))
{
Scanner scanner = new Scanner(Console.In);
TreeBuilder builder = new TreeBuilder();
Parser parser = new Parser(scanner, builder);
Node root = (Node)parser.parseExp();
return(Void.getInstance());
}
if (symName.Equals("write"))
{
arg1.print(0);
return(Void.getInstance());
}
if (symName.Equals("display"))
{
((StringLit)arg1).displayPrint();
return(Void.getInstance());
}
if (symName.Equals("eval"))
{
return(arg1.eval((Environment)arg2));
}
if (symName.Equals("apply"))
{
return(arg1.apply(arg2));
}
return(Void.getInstance());
}