LispEval.cpp

#include "LispObj.h"
#include "LispNil.h"
#include "LispChar.h"
#include "LispCons.h"
#include "LispEnv.h"
#include "LispFixNum.h"
#include "LispFloatNum.h"
#include "LispString.h"
#include "LispSymbol.h"
#include "LispPrimitive.h"
#include "LispEval.h"
#include "LispLambda.h"

namespace Lisp {

LispObjRef Eval::operator()(LispObjRef obj, LispEnvRef env, bool fplace) {

	// trivial case :-)
	if (is_nil(obj))
	  return nil;
	// constant literal 
	if (is_char(obj) ||	is_fixnum(obj) || is_floatnum(obj) || is_string(obj) || is_primitive(obj))
	  return obj;
	// symbol lookup
	if (is_symbol(obj)) {
		LispObjRef result = fplace ? env->fref(get_ctype<SymbolType>(obj).name) : env->ref(get_ctype<SymbolType>(obj).name);
		return result;
	}
	// cons cell
	if (is_cons(obj)) 
	{
		// must be function invocation -- function symbol
		LispObjRef fnsym(eval(car(obj), env, is_symbol(car(obj))));
		if ((is_symbol(fnsym)) | (is_primitive(fnsym)))
		{	
			// it's a function
			if (is_primitive(fnsym)) {
				CPrim cfn = (CPrim)(boost::get<PrimType>(*fnsym));
				// call it on the cdr
				LispObjRef result = cfn(cdr(obj), env);
				return result;
			}
		}
		// else -- apply			
		if (is_lambda(fnsym)) {
			// fnsym is the lambda
			// cdr(obj) is the values applied
			LispObjRef params = cdr(obj);
			LispEnvRef newEnv(new LispEnv(env));
			LispObjRef args = get_ctype<LambdaType>(fnsym).args;
			while (!is_nil(args)) {
				LispObjRef param = car(params);
				LispObjRef arg = car(args);
				if (is_symbol(arg)) {
					newEnv->set(get_ctype<SymbolType>(arg).name,param);
				}
				if (is_cons(params))
					params = cdr(params);
				args = cdr(args);
			}
			return eval(get_ctype<LambdaType>(fnsym).body, newEnv);
			
		}		
	} 
	return nil;		
  };
}