public override Node eval(Node t, Environment env)
{
Node var = t.getCdr().getCar();
Node val = t.getCdr().getCdr().getCar();
env.define(var, val);
return(Void.getInstance());
}
public override Node eval(Node t, Environment env)
{
Node car1 = t.getCdr().getCar();
Node car2 = t.getCdr().getCdr().getCar();
if (car1.isSymbol())
{
// if first arg is not a list, define variable
env.define(car1, car2);
}
else
{
// if first arg is list, define function and function body
Cons funcbody = new Cons(car1.getCdr(), t.getCdr().getCdr());
Node closureFun = new Cons(new Ident("lambda"), funcbody).eval(env);
env.define(car1.getCar(), closureFun);
}
return(Void.getInstance());
}
public override Node eval(Node 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());
}
// sets first as function, args as function arguments, and performs apply() on first
public override Node eval(Node t, Environment env)
{
Node first = t.getCar();
Node args = t.getCdr();
if (!(args is Nil))
{
if (t.getCdr().getCar().isSymbol())
{
args = getArgs(t.getCdr(), env);
}
if (t.getCdr().getCar().isPair() && !t.getCdr().getCar().getCar().isNumber())
{
args = new Cons(t.getCdr().getCar().eval(env), Nil.getInstance());
}
if (env.lookup(first).isProcedure())
{
first = env.lookup(first);
Node temp = first.apply(args);
return(temp);
}
else
{
Console.WriteLine("Error: Procedure not specified.");
}
}
else
{
if (env.lookup(first).isProcedure())
{
first = env.lookup(first);
Node temp = first.apply(Nil.getInstance());
return(temp);
}
}
return(Void.getInstance());
}
public override Node eval(Node exp, Environment env)
{
int num = Node.length(exp);
if (num <= 2)
{
Console.Error.WriteLine("Error: invalid define expression");
return(Nil.getInstance());
}
Node car1 = exp.getCdr().getCar();
if (car1.isSymbol() && num == 3)
{
Node car2 = exp.getCdr().getCdr().getCar();
env.define(car1, car2.eval(env));
return(Void.getInstance());
}
if (!car1.isPair())
{
Console.Error.WriteLine("Error: invalid expression");
return((Node)Nil.getInstance());
}
Node car3 = car1.getCar();
Node cdr1 = car1.getCdr();
Node cdr2 = exp.getCdr().getCdr();
if (!car3.isSymbol() || !isValid(cdr1))
{
Console.Error.WriteLine("Error: ill-formed definition");
return((Node)Nil.getInstance());
}
Node node = (Node) new Cons((Node) new Ident("lambda"), (Node) new Cons(cdr1, cdr2));
env.define(car3, node.eval(env));
return((Node)Void.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());
}