/** Replace the old cons cell with the macro expansion, and return it. **/
public Pair expand(Scheme interpreter, Pair oldPair, Object args)
{
Object expansion = apply(interpreter, args);
if (expansion is Pair)
{
oldPair.first = ((Pair)expansion).first;
oldPair.rest = ((Pair)expansion).rest;
}
else
{
oldPair.first = "begin";
oldPair.rest = cons(expansion, null);
}
return oldPair;
}
/** Map proc over a list of lists of args, in the given interpreter.
* If result is non-null, accumulate the results of each call there
* and return that at the end. Otherwise, just return null. **/
static Pair map(Procedure proc, Object args, Scheme interp, Pair result)
{
Pair accum = result;
if (rest(args) == null)
{
args = first(args);
while (args is Pair)
{
Object x = proc.apply(interp, list(first(args)));
if (accum != null) accum = (Pair) (accum.rest = list(x));
args = rest(args);
}
}
else
{
Procedure car = Procedure.proc(interp.eval("car"));
Procedure cdr = Procedure.proc(interp.eval("cdr"));
while (first(args) is Pair)
{
Object x = proc.apply(interp, map(car, list(args), interp, list(null)));
if (accum != null) accum = (Pair) (accum.rest = list(x));
args = map(cdr, list(args), interp, list(null));
}
}
return (Pair)rest(result);
}