From ab23395b1fc88bbc63bef88de3477cc316857ace Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Thu, 14 Oct 2021 10:29:55 +0200
Subject: Add initial lambda implementation

---
 src/bootstrap/primitives.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)

(limited to 'src/bootstrap/primitives.c')

diff --git a/src/bootstrap/primitives.c b/src/bootstrap/primitives.c
index 3afeef6..461799e 100644
--- a/src/bootstrap/primitives.c
+++ b/src/bootstrap/primitives.c
@@ -1,8 +1,10 @@
 Object *
 eval(Environment* env, Object *root) {
+tailcall:
     switch (root->type) {
         case OBJ_TYPE_ERR:
         case OBJ_TYPE_PROCEDURE:
+        case OBJ_TYPE_LAMBDA:
         case OBJ_TYPE_FIXNUM:
         case OBJ_TYPE_BOOL:
         case OBJ_TYPE_NIL:
@@ -39,6 +41,52 @@ eval(Environment* env, Object *root) {
                 });
                 return obj_err;
             }
+            Object* lambda = eval(env, root->car);
+            if (lambda->type == OBJ_TYPE_LAMBDA) {
+                Object *fun = lambda;
+                Object *args = root->cdr;
+                Object *params = fun->args;
+                while (params != obj_nil) {
+                    if (args == obj_nil) {
+                        error_push((Error){
+                            .type = ERR_TYPE_RUNTIME,
+                            .value = ERR_NOT_ENOUGH_ARGS,
+                        });
+                        return obj_err;
+                    }
+                    Object *symbol = params->car;
+                    Object *value = eval(env, args->car);
+                    if (value == obj_err) {
+                        return obj_err;
+                    }
+                    if (value == obj_nil) {
+                        error_push((Error){
+                            .type = ERR_TYPE_RUNTIME,
+                            .value = ERR_NOT_ENOUGH_ARGS,
+                        });
+                        return obj_err;
+                    }
+                    ssize_t index = env_symbol_index_in_current_env(fun->env, symbol);
+                    if (index == -1) {
+                        env_add_symbol(fun->env, obj_duplicate(symbol), obj_duplicate(value));
+                    } else {
+                        fun->env->buf[index].value = obj_duplicate(value);
+                    }
+                    args = args->cdr;
+                    params = params->cdr;
+                }
+                if (args != obj_nil) {
+                    error_push((Error){
+                        .type = ERR_TYPE_RUNTIME,
+                        .value = ERR_TOO_MANY_ARGS,
+                    });
+                    return obj_err;
+                }
+
+                env = fun->env;
+                root = fun->body;
+                goto tailcall;
+            }
         } break;
     }
 
@@ -692,6 +740,31 @@ proc_set(Environment *env, Object *obj) {
     return obj_nil;
 }
 
+Object *
+proc_lambda(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 *args = obj->car;
+    if (args != obj_nil && args->type != OBJ_TYPE_PAIR) {
+        error_push((Error){
+            .type = ERR_TYPE_RUNTIME,
+            .value = ERR_WRONG_ARG_TYPE,
+        });
+        return obj_err;
+    }
+    Object *body = obj->cdr->car;
+    Object *fun = alloc_object(OBJ_TYPE_LAMBDA);
+    fun->args = obj_duplicate(args);
+    fun->body = obj_duplicate(body);
+    fun->env = env_create(env);
+    return fun;
+}
+
 
 //
 // Evaluation.
@@ -709,6 +782,10 @@ proc_eval(Environment *env, Object *obj) {
     return eval(env, eval(env, obj->car));
 }
 
+//
+// Runtime configuration options.
+//
+
 Object *
 proc_supress_errors(Environment *env, Object *obj) {
     Object *car = extract_car_with_type(env, obj, OBJ_TYPE_BOOL);
-- 
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