public override Node eval(Node t, Environment env)
{
//arg1: set!
//arg2: variable
//arg3: value
env.assign(t.getCdr().getCar(), t.getCdr().getCdr().getCar().eval(env));
return new StringLit("set done");
}
public override Node eval(Environment env, Node args)
{
Node expr1 = args.getCar();
if (args.getCdr().isNull() == true)
{
return(new StringLit("Error: Only 1 argument passed to 'set!.'"));
}
else if (args.getCdr().getCdr().isNull() == false)
{
return(new StringLit("Error: Too many arguments passed to 'set!.'"));
}
// Is this defining a function?
else if (expr1.isPair() == true)
{
if (expr1.getCar().isSymbol() == true)
{
// Construct the lambda expression
Node formalsAndBody = new Cons(expr1.getCdr(), args.getCdr());
Node lambdaExpr = new Cons(new Ident("lambda"), formalsAndBody);
// set!.apply()
return(env.assign(expr1.getCar(), lambdaExpr.eval(env)));
}
else
{
return(new StringLit("Error: First argument to 'set!' must be a <variable>"));
}
}
else
{
if (expr1.isSymbol() == true)
{
// set!.apply()
return(env.assign(expr1, args.getCdr().getCar().eval(env)));
}
else
{
return(new StringLit("Error: First argument to 'set!' must be a <variable>"));
}
}
}
public override Node eval(Node exp, Environment env)
{
if (Node.length(exp) != 3)
{
Console.Error.WriteLine("Error: invalid set expression");
return((Node)Nil.getInstance());
}
Node var = exp.getCdr().getCar();
Node varExp = exp.getCdr().getCdr().getCar();
env.assign(var, varExp.eval(env));
return(Unspecific.getInstance());
}
public Node eval(Node t, Environment e)
{
Node current = t.getCdr().getCar();
if (!current.isSymbol())
{
Console.Error.WriteLine("Error: Not an identifier");
return Nil.getInstance();
}
// insert some methods about env, kinda confusing/binding stuff
Node final = t.getCdr().getCdr().getCar();
final = final.eval(final, e);
e.assign(current, final);
return new StringLit("; " + current.getName() + " - updated.");
}
// - assign to a name (for implementing set!)
// if the name exists in the innermost scope, update the value
// if it doesn't exist, perform the assignment in the enclosing scope
// if we don't find the name, it is an error
public void assign(Node id, Node val)
{
if (this.lookup(id) != null)
{
frame.setCdr(new Cons(val, null));
}
else if (env.lookup(id) != null)
{
env.assign(id, val);
}
else
{
Console.Error.WriteLine("Name not found Env.assign: " + id.getName());
}
}
public Node eval(Node t, Environment e)
{
Node current = t.getCdr().getCar();
if (!current.isSymbol())
{
Console.Error.WriteLine("Error: Not an identifier");
return(Nil.getInstance());
}
// insert some methods about env, kinda confusing/binding stuff
Node final = t.getCdr().getCdr().getCar();
final = final.eval(final, e);
e.assign(current, final);
return(new StringLit("; " + current.getName() + " - updated."));
}
public void assign(Node id, Node val)
{
Node node = find(id, frame);
if (node == null && env == null)
{
Console.Error.WriteLine("Undefined variable " + id.getName());
}
else if (node == null)
{
env.assign(id, val);
}
else
{
node.setCar(val);
}
}
public void assign(Node id, Node val)
{
// if the term and the env are null, variable undefined (error state)
if (find(id, val) == null && env == null)
{
Console.Error.WriteLine("undefined variable: " + id.getName());
}
else if (find(id, val) == null)
{
// else, if the term is undefined (and env is), assign the term to env
env.assign(id, val);
}
else
{
// else, if both term and env are defined, set the car of the term to val
find(id, frame).setCar(val);
}
}
// from prof email: The method assign() is for implementing Set.eval().
// It modifies the value of an existing variable.
// The recursive structure is the same as for lookup(), except that after calling find(),
// the value should be updated instead of returned
public void assign(Node id, Node val)
{
// DONE :: implement this function
Node value = find(id, frame);
if (value.isNull() && env == null)
{
Console.Error.WriteLine("undefined variable " + id.getName());
}
else if (value.isNull())
{
env.assign(id, val);
}
else
{
value.setCar(val);
}
}
public override Node eval(Node exp, Environment env)
{
int num = Util.expLength(exp);
//(set-cdr! (assq ’x (car env)) (list 15)), need length 3
bool flag = num != 3;
Node instance;
if (flag)
{
Console.Error.WriteLine("Error: invalid expression");
instance = Nil.getInstance();
}
else
{
Node car = exp.getCdr().getCar();
//Console.WriteLine(car);
Node car2 = exp.getCdr().getCdr().getCar();
//Console.Writeline(car2)
env.assign(car, car2.eval(env));
instance = Unspecific.getInstance();
}
return instance;
}
public override Node eval(Node exp, Environment env)
{
int numArgs = 0;
Node expCdr = exp.getCdr();
while (!expCdr.isNull())
{
numArgs++;
expCdr = expCdr.getCdr();
}
if (numArgs != 2)
{
Console.Error.WriteLine("Error: invalid expression");
return(Nil.getInstance());
}
Node arg1 = exp.getCdr().getCar();
Node arg2 = exp.getCdr().getCdr().getCar();
env.assign(arg1, arg2.eval(env));
return(new StringLit("#{Unspecific}", false));
}
