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#include <stdlib.h>
#include <stdio.h>
#include <readline/readline.h>
#include <readline/history.h>
#include "lisp.h"
#include "lex.yy.h"
#include "lisp.tab.h"
value *make_int(int i) {
value *val = malloc(sizeof(value));
val->type = VT_INT;
val->as.i = i;
return val;
}
value *make_double(double d) {
value *val = malloc(sizeof(value));
val->type = VT_DOUBLE;
val->as.d = d;
return val;
}
value *make_symbol(const char *s) {
value *val = malloc(sizeof(value));
val->type = VT_SYMBOL;
val->as.sym = s;
return val;
}
value *make_string(const char *s) {
value *val = malloc(sizeof(value));
val->type = VT_STRING;
val->as.str = s;
return val;
}
value *make_nil() {
value *val = malloc(sizeof(value));
val->type = VT_NIL;
return val;
}
value *make_lambda(env *e, value *params, value *body) {
printf("making lambda:\n");
value *l = malloc(sizeof(value));
l->type = VT_LAMBDA;
l->as.lambda.params = params;
printf("params: ");
print_value(params);
l->as.lambda.body = body;
printf("\nbody: ");
print_value(body);
printf("\n");
l->as.lambda.env = e;
return l;
}
value *cons(value *car, value *cdr) {
value *val = malloc(sizeof(value));
val->type = VT_PAIR;
val->as.pair.car = car;
val->as.pair.cdr = cdr;
return val;
}
value *car(value *cons) {
//TODO: more robust implementation with error catching
return cons->as.pair.car;
}
value *cdr(value *cons) {
//TODO: more robust implementation with error catching
return cons->as.pair.cdr;
}
void *print_value(value *val){
char *str;
switch (val->type) {
case VT_INT:
printf("%d", val->as.i);
break;
case VT_DOUBLE:
printf("%f", val->as.d);
break;
case VT_SYMBOL:
printf("%s", val->as.sym);
break;
case VT_STRING:
printf("\"%s\"", val->as.str);
break;
case VT_NIL:
printf("()");
break;
case VT_PAIR:
printf("(");
print_value(val->as.pair.car);
printf(" . ");
print_value(val->as.pair.cdr);
printf(")");
break;
case VT_LAMBDA:
printf("(λ ");
print_value(val->as.lambda.params);
printf(" ");
print_value(val->as.lambda.body);
printf(")");
default:
}
return val;
}
env *env_create(env *parent) {
env *e = malloc(sizeof(env));
e->symbol = NULL;
e->value = NULL;
e->next = NULL;
e->parent = parent;
return e;
}
env *env_define(env *e, const char *sym, value *val) {
if (e->next) {
return env_define(e->next, sym, val);
}
env *new = malloc(sizeof(env));
new->symbol = strdup(sym);
new->value = val;
new->next = NULL;
new->parent = e->parent;
e->next = new;
return new;
}
value *env_lookup(env *e, const char *sym) {
if (e->symbol && !strcmp(e->symbol, sym)) {
return e->value;
}
if (e->next) {
return env_lookup(e->next, sym);
}
if (e->parent) {
return env_lookup(e->parent, sym);
}
return NULL;
}
value *eval(env *e, value *v) {
value *found;
if (v->type == VT_NIL) {
return v;
}
if (v->type == VT_SYMBOL &&
(found = env_lookup(e, v->as.sym))) {
return found;
}
if (v->type == VT_SYMBOL) {
printf("symbol %s not found\n", v->as.sym);
return v;
}
if (v->type == VT_PAIR) {
return eval_pair(e, v);
}
return v;
}
value *eval_pair(env *e, value *v) {
value *head = car(v);
value *tail = cdr(v);
value *head_eval = eval(e, head);
if (head_eval->type == VT_LAMBDA) {
apply(head_eval, tail);
}
if (!strcmp(head->as.str, "define")) {
value *defargs = tail;
value *defname = car(defargs);
value *defval = eval(e, car(cdr(defargs)));
if (defname->type != VT_SYMBOL) {
printf("error, expected symbol, found: ");
print_value(defname);
printf("\n");
return v;
}
env_define(e, defname->as.sym, defval);
}
if (!strcmp(head->as.str, "lambda") ||
!strcmp(head->as.str, "\\") ||
!strcmp(head->as.str, "λ")) {
value *params = car(tail);
value *body = car(cdr(tail));
return make_lambda(e, params, body);
}
return v;
}
value *apply(value *lval, value *args) {
env *sub_env = env_create(lval->as.lambda.env);
value *params = lval->as.lambda.params;
value *arg = args;
while (params->type == VT_PAIR && arg->type == VT_PAIR) {
env_define(sub_env,
car(params)->as.sym,
eval(lval->as.lambda.env, car(arg)));
params = cdr(params);
arg = cdr(arg);
}
return eval(sub_env, lval->as.lambda.body);
}
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