From d38ae947933fe26773a810d91fba3b23766d4d92 Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Wed, 13 Oct 2021 20:46:26 +0200
Subject: Add set! and eval procedures

---
 src/bootstrap/environment.c | 13 +++------
 src/bootstrap/main.c        |  2 ++
 src/bootstrap/primitives.c  | 68 ++++++++++++++++++++++++++++++++++++++++++---
 3 files changed, 70 insertions(+), 13 deletions(-)

diff --git a/src/bootstrap/environment.c b/src/bootstrap/environment.c
index d4e9f86..99dd7fd 100644
--- a/src/bootstrap/environment.c
+++ b/src/bootstrap/environment.c
@@ -60,18 +60,13 @@ env_lookup(Environment *env, Object *symbol) {
     return obj_err;
 }
 
-void
-env_update_symbol(Environment *env, Object *symbol, Object *value) {
-    // Try to find an existing symbol in the current environment.
+ssize_t
+env_symbol_index_in_current_env(Environment *env, Object *symbol) {
     for (size_t i = 0; i < env->size; i++) {
         EnvEntry entry = env->buf[i];
         if (obj_eq(symbol, entry.symbol)) {
-            env->buf[i].value = value;
-            return;
+            return i;
         }
     }
-    // If we don't find the symbol, add a new entry.
-    env_add_symbol(env, symbol, value);
+    return -1;
 }
-
-// TODO: Free env function.
diff --git a/src/bootstrap/main.c b/src/bootstrap/main.c
index e8e530d..052f1c0 100755
--- a/src/bootstrap/main.c
+++ b/src/bootstrap/main.c
@@ -40,6 +40,7 @@ init(void) {
     MAKE_ENV_VAR(global_env, "nil", obj_nil);
 
     // Primitive procedures.
+    MAKE_ENV_PROC(global_env, "eval", proc_eval);
     MAKE_ENV_PROC(global_env, "quote", proc_quote);
     MAKE_ENV_PROC(global_env, "car", proc_car);
     MAKE_ENV_PROC(global_env, "cdr", proc_cdr);
@@ -72,6 +73,7 @@ init(void) {
     MAKE_ENV_PROC(global_env, "=", proc_num_equal);
     MAKE_ENV_PROC(global_env, "eq?", proc_equal);
     MAKE_ENV_PROC(global_env, "def", proc_define);
+    MAKE_ENV_PROC(global_env, "set!", proc_set);
 }
 
 void
diff --git a/src/bootstrap/primitives.c b/src/bootstrap/primitives.c
index af8e9da..a3b69f6 100644
--- a/src/bootstrap/primitives.c
+++ b/src/bootstrap/primitives.c
@@ -630,15 +630,75 @@ proc_define(Environment *env, Object *obj) {
     }
 
     // Make a copy of the symbol and to make them permanent in the environment.
-    env_update_symbol(env, obj_duplicate(symbol), obj_duplicate(value));
+    ssize_t index = env_symbol_index_in_current_env(env, symbol);
+    if (index == -1) {
+        env_add_symbol(env, obj_duplicate(symbol), obj_duplicate(value));
+    } else {
+        env->buf[index].value = obj_duplicate(value);
+    }
+    return obj_nil;
+}
+
+Object *
+proc_set(Environment *env, Object *obj) {
+    if (obj == obj_nil || obj->cdr == obj_nil) {
+        error_push((Error){
+            .type = ERR_TYPE_RUNTIME,
+            .value = ERR_NOT_ENOUGH_ARGS,
+        });
+        return obj_err;
+    }
+
+    Object *symbol = obj->car;
+    if (symbol->type != OBJ_TYPE_SYMBOL) {
+        error_push((Error){
+            .type = ERR_TYPE_RUNTIME,
+            .value = ERR_WRONG_ARG_TYPE,
+        });
+        return obj_err;
+    }
+
+    Object *value = eval(env, obj->cdr->car);
+    if (value == obj_err) {
+        return obj_err;
+    }
+
+    ssize_t index = env_symbol_index_in_current_env(env, symbol);
+    if (index == -1) {
+        error_push((Error){
+            .type = ERR_TYPE_RUNTIME,
+            .value = ERR_SYMBOL_NOT_FOUND,
+        });
+        return obj_err;
+    }
+
+    env->buf[index].value = obj_duplicate(value);
     return obj_nil;
 }
 
+
+//
+// Evaluation.
+//
+
+Object *
+proc_eval(Environment *env, Object *obj) {
+    if (obj == obj_nil) {
+        error_push((Error){
+            .type = ERR_TYPE_RUNTIME,
+            .value = ERR_NOT_ENOUGH_ARGS,
+        });
+        return obj_err;
+    }
+    return eval(env, eval(env, obj->car));
+}
+
+// TODO: map
+// TODO: apply
+// TODO: filter
+
 // TODO: fixnum left/right shift, mask, invert
 // TODO: add primitives for type transforms: string->symbol, symbol->string, etc
 // TODO: implement support for semi-quotes
 // TODO: LAMBDA
 // TODO: let
-// TODO: Revise all instances where we are returning an object, since currently
-// we may be returning a pointer to an object instead of a new one. Check also
-// on eval function and everytime we do make_xxx(obj).
-- 
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