From e6e501c5a3774fb5a1aba5c427e2884ab253ea04 Mon Sep 17 00:00:00 2001
From: Aryadev Chavali <aryadev@aryadevchavali.com>
Date: Fri, 13 Feb 2026 00:06:57 +0000
Subject: [PATCH] lisp: tag_generic, tag_sizeof, and lisp_sizeof

---
 include/alisp/lisp.h |  3 +++
 src/lisp.c           | 45 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/include/alisp/lisp.h b/include/alisp/lisp.h
index ba77720..31d5ea3 100644
--- a/include/alisp/lisp.h
+++ b/include/alisp/lisp.h
@@ -65,6 +65,7 @@ lisp_t *tag_int(const i64);
 lisp_t *tag_sym(const char *);
 lisp_t *tag_cons(const cons_t *);
 lisp_t *tag_vec(const vec_t *);
+lisp_t *tag_generic(void *, tag_t);
 
 i64 as_int(lisp_t *);
 char *as_sym(lisp_t *);
@@ -75,6 +76,8 @@ vec_t *as_vec(lisp_t *);
 #define CDR(L) (as_cons(L)->cdr)
 
 void lisp_print(FILE *, lisp_t *);
+u64 tag_sizeof(tag_t);
+u64 lisp_sizeof(lisp_t *);
 
 #endif
 
diff --git a/src/lisp.c b/src/lisp.c
index 4caf67c..f9ce6d4 100644
--- a/src/lisp.c
+++ b/src/lisp.c
@@ -30,6 +30,26 @@ lisp_t *tag_cons(const cons_t *cons)
   return TAG((u64)cons, CONS);
 }
 
+lisp_t *tag_generic(void *ptr, tag_t type)
+{
+  switch (type)
+  {
+  case TAG_NIL:
+    return NIL;
+  case TAG_INT:
+    return tag_int((i64)ptr);
+  case TAG_SYM:
+    return tag_sym(ptr);
+  case TAG_CONS:
+    return tag_cons(ptr);
+  case TAG_VEC:
+    return tag_vec(ptr);
+  default:
+    FAIL("Unreachable");
+    return NIL;
+  }
+}
+
 tag_t get_tag(const lisp_t *lisp)
 {
   static_assert(NUM_TAGS == 5);
@@ -165,6 +185,31 @@ void lisp_print(FILE *fp, lisp_t *lisp)
   }
 }
 
+u64 tag_sizeof(tag_t tag)
+{
+  switch (tag)
+  {
+  case TAG_NIL:
+    return 0;
+  case TAG_INT:
+  case TAG_SYM:
+    return sizeof(lisp_t *);
+  case TAG_CONS:
+    return sizeof(cons_t);
+  case TAG_VEC:
+    return sizeof(vec_t);
+  case NUM_TAGS:
+  default:
+    FAIL("Unreachable");
+    return 0;
+  }
+}
+
+u64 lisp_sizeof(lisp_t *lisp)
+{
+  return tag_sizeof(get_tag(lisp));
+}
+
 /* Copyright (C) 2025, 2026 Aryadev Chavali
 
  * This program is distributed in the hope that it will be useful, but WITHOUT