3 files changed, 103 insertions, 14 deletions

diff --git a/lisp.c b/lisp.c
index cbd92b2..95d8670 100644
--- a/lisp.c
+++ b/lisp.c
@@ -48,7 +48,7 @@ value *cons(value *car, value *cdr) {
 	return val;
 }
 
-void *print_val(value *val){
+void *print_value(value *val){
 	char *str;
 	switch (val->type) {
 		case VALTYPE_INT:
@@ -73,9 +73,9 @@ void *print_val(value *val){
 
 		case VALTYPE_PAIR:
 			printf("(");
-			print_val(val->as.pair.car);
+			print_value(val->as.pair.car);
 			printf(" . ");
-			print_val(val->as.pair.cdr);
+			print_value(val->as.pair.cdr);
 			printf(")");
 		default:
 	}
@@ -83,13 +83,89 @@ void *print_val(value *val){
 	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;
+}
+
 int main(void) {
-    char* line;
-    while ((line = readline("λ > ")) != NULL) {
-        if (*line) add_history(line);
-        yy_scan_string(line);
-        yyparse();
-        free(line);
-    }
-    return 0;
+	/* TEST; DANKE CHATGPT
+	// create global environment
+	env *global = env_create(NULL);
+	// define some variables
+	env_define(global, "x", make_int(10));
+	env_define(global, "y", make_int(42));
+	
+	// lookup variables
+	value *vx = env_lookup(global, "x");
+	value *vy = env_lookup(global, "y");
+	value *vz = env_lookup(global, "z"); // undefined
+	//
+	if (vx) {
+		printf("x = ");
+		print_value(vx);
+		printf("\n");
+	}
+	if (vx) {
+		printf("y = ");
+		print_value(vy);
+		printf("\n");
+	}
+	if (vz) {
+		printf("z = ");
+		print_value(vz);
+		printf("\n");
+	}
+
+	// create nested environment
+	env *local = env_create(global);
+	env_define(local, "x", make_int(99)); // shadow global x
+	
+	value *lx = env_lookup(local, "x"); // should find local
+	value *ly = env_lookup(local, "y"); // should find global
+	
+	printf("local x = %d\n", lx ? lx->as.i : -1);
+	printf("local y = %d\n", ly ? ly->as.i : -1);
+	*/
+	// START REPL
+	char* line;
+	while ((line = readline("λ > ")) != NULL) {
+		if (*line) {
+			add_history(line);
+		}
+		yy_scan_string(line);
+		yyparse();
+		free(line);
+	}
+	return 0;
 }
diff --git a/lisp.h b/lisp.h
index 535bc50..4053bd5 100644
--- a/lisp.h
+++ b/lisp.h
@@ -32,6 +32,19 @@ value *make_string(const char *str);
 value *make_nil();
 value *cons(value *car, value *cdr);
 
-void *print_val(value *val);
+void *print_value(value *val);
+// environments, TODO: make this use hashtable
+// symbol->val
+typedef struct env env;
+typedef struct env {
+	const char *symbol;
+	value *value;
+	env *next;
+	env *parent;
+} env;
+
+env *env_create(env *parent);
+env *env_define(env *e, const char *sym, value *val);
+value *env_lookup(env *e, const char *sym);
 
 #endif
diff --git a/lisp.y b/lisp.y
index da1b315..93dd877 100644
--- a/lisp.y
+++ b/lisp.y
@@ -28,8 +28,8 @@ static int is_integer(double x) {
 %start sexprs
 
 %%
-sexprs: sexpr { print_val($1); printf("\n"); }
-      | sexprs sexpr { print_val($2); printf("\n"); };
+sexprs: sexpr { print_value($1); printf("\n"); }
+      | sexprs sexpr { print_value($2); printf("\n"); };
 
 sexpr:  atom
      |  list