Cleanup if call in eval function

3 files changed, 37 insertions, 53 deletions

diff --git a/src/bootstrap/gc.c b/src/bootstrap/gc.c
index 5f023bc..11a1f5a 100644
--- a/src/bootstrap/gc.c
+++ b/src/bootstrap/gc.c
@@ -270,7 +270,7 @@ alloc_object(ObjectType type) {
             // references! Should we work with offsets all the way?  That is for
             // cdr and car? Should we have a utility function? All in all, we
             // need to refactor the codebase first to work with pointer offsets
-            // rather than objects.  This issue is very important, if we are in
+            // rather than objects. This issue is very important, if we are in
             // the middle of an operation that tries to allocate memory but we
             // had saved pointers to some object, the pointer references may be
             // invalidated, crashing or worse, silently returning garbage! Let's
diff --git a/src/bootstrap/main.c b/src/bootstrap/main.c
index bf2354b..2d24f92 100755
--- a/src/bootstrap/main.c
+++ b/src/bootstrap/main.c
@@ -37,11 +37,13 @@ init(void) {
     obj_false = alloc_object(OBJ_TYPE_BOOL);
     obj_err = alloc_object(OBJ_TYPE_ERR);
     obj_quote = make_symbol((StringView){"quote", 5});
+    proc_if = alloc_object(OBJ_TYPE_ERR);
     push_root(obj_nil);
     push_root(obj_true);
     push_root(obj_false);
     push_root(obj_err);
     push_root(obj_quote);
+    push_root(proc_if);
 
     // Global environment.
     global_env = env_create(NULL);
@@ -52,6 +54,7 @@ init(void) {
     // Primitive symbols.
     MAKE_ENV_VAR(global_env, "else", obj_true);
     MAKE_ENV_VAR(global_env, "nil", obj_nil);
+    MAKE_ENV_VAR(global_env, "if", proc_if);
 
     // Primitive procedures.
     MAKE_ENV_PROC(global_env, "eval", proc_eval);
@@ -79,7 +82,6 @@ init(void) {
     MAKE_ENV_PROC(global_env, "not", proc_not);
     MAKE_ENV_PROC(global_env, "and", proc_and);
     MAKE_ENV_PROC(global_env, "or", proc_or);
-    MAKE_ENV_PROC(global_env, "if", proc_if);
     MAKE_ENV_PROC(global_env, "cond", proc_cond);
     MAKE_ENV_PROC(global_env, "<", proc_num_less_than);
     MAKE_ENV_PROC(global_env, "<=", proc_num_lesseq_than);
diff --git a/src/bootstrap/primitives.c b/src/bootstrap/primitives.c
index 0403e3a..ab147d4 100644
--- a/src/bootstrap/primitives.c
+++ b/src/bootstrap/primitives.c
@@ -1,6 +1,5 @@
 #define DEBUG_OBJ(MSG,OBJ) printf((MSG)); display(OBJ); printf("\n");
-
-Object * proc_if(Environment *env, Object *obj);
+static Object *proc_if;
 
 Object *
 eval(Environment *env, Object *root) {
@@ -41,32 +40,34 @@ eval_start:
                     });
                     return obj_err;
                 }
-                if (val->type == OBJ_TYPE_PROCEDURE) {
-                    // TODO: This is very messy, needs refactoring.
-                    if (val->proc == proc_if) {
-                        Object *obj = root->cdr;
-                        if (obj == obj_nil || obj->cdr == obj_nil) {
-                            error_push((Error){
-                                .type = ERR_TYPE_RUNTIME,
-                                .value = ERR_NOT_ENOUGH_ARGS,
-                            });
-                            return obj_err;
-                        }
-                        Object *car = obj->car;
-                        Object *cdr = obj->cdr;
-                        Object *condition = eval(env, car);
-                        if (condition == obj_err) {
-                            return obj_err;
-                        }
-                        if (condition == obj_true) {
-                            root = cdr->car;
-                        } else if (cdr->cdr != obj_nil) {
-                            root = cdr->cdr->car;
-                        } else {
-                            return obj_nil;
-                        }
-                        goto eval_start;
+
+                // Primitive `if` procedure with TCO.
+                if (val == proc_if) {
+                    Object *obj = root->cdr;
+                    if (obj == obj_nil || obj->cdr == obj_nil) {
+                        error_push((Error){
+                            .type = ERR_TYPE_RUNTIME,
+                            .value = ERR_NOT_ENOUGH_ARGS,
+                        });
+                        return obj_err;
                     }
+                    Object *car = obj->car;
+                    Object *cdr = obj->cdr;
+                    Object *condition = eval(env, car);
+                    if (condition == obj_err) {
+                        return obj_err;
+                    }
+                    if (condition == obj_true) {
+                        root = cdr->car;
+                    } else if (cdr->cdr != obj_nil) {
+                        root = cdr->cdr->car;
+                    } else {
+                        return obj_nil;
+                    }
+                    goto eval_start;
+                }
+
+                if (val->type == OBJ_TYPE_PROCEDURE) {
                     ret = val->proc(env, root->cdr);
                     goto eval_success;
                 }
@@ -138,6 +139,11 @@ eval_lambda:
                 root = root->car;
                 goto eval_start;
             }
+            error_push((Error){
+                .type = ERR_TYPE_RUNTIME,
+                .value = ERR_OBJ_NOT_CALLABLE,
+            });
+            return obj_err;
         } break;
     }
 
@@ -483,30 +489,6 @@ proc_or(Environment *env, Object *obj) {
 }
 
 Object *
-proc_if(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 *car = obj->car;
-    Object *cdr = obj->cdr;
-    Object *condition = eval(env, car);
-    if (condition == obj_err) {
-        return obj_err;
-    }
-    if (condition == obj_true) {
-        return eval(env, cdr->car);
-    }
-    if (cdr->cdr != obj_nil) {
-        return eval(env, cdr->cdr->car);
-    }
-    return obj_nil;
-}
-
-Object *
 proc_cond(Environment *env, Object *obj) {
     if (obj == obj_nil) {
         error_push((Error){