//need to check to see if binding for x (in this case 'identifier') already exists
public override Node eval(Node t, Environment env)
{
//works for (x 3) but does it work for twice (lambda (f x) (f.............))?
Node identifier = t.getCdr().getCar();
Node value = t.getCdr().getCdr().getCar();
if ((identifier.isSymbol())) //this is for if it is in the form of (define x 3), here x is not a function
{
env.define(identifier,value);
}
else
{
Closure idFunction = new Closure(new Cons(t.getCdr().getCar().getCdr(), t.getCdr().getCdr()), env);
env.define(identifier.getCar(), idFunction);
}
return null;
}
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);
}
// 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());
}
}