From b4ed9d489f7401ee0cd8a6d6e8ce9d97f0dc7833 Mon Sep 17 00:00:00 2001
From: Phil Burk <philburk@mobileer.com>
Date: Sun, 4 Dec 2022 13:25:39 -0800
Subject: [PATCH] Add [DEFINED] and [UNDEFINED] (#127)

Also add tests.

Fixes #111
---
 fth/condcomp.fth | 12 +++++++++++-
 fth/t_corex.fth  | 14 ++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/fth/condcomp.fth b/fth/condcomp.fth
index dc65c6b..762cde8 100644
--- a/fth/condcomp.fth
+++ b/fth/condcomp.fth
@@ -46,5 +46,15 @@ anew task-condcomp.fth
 
 : EXISTS? ( <name> -- flag , true if defined )
     bl word find
-    swap drop
+    nip 0<>
+; immediate
+
+: [DEFINED] ( <name> -- flag , true if defined, ANS )
+    bl word find
+    nip 0<>
+; immediate
+
+: [UNDEFINED] ( <name> -- flag , true if not defined, ANS )
+    bl word find
+    nip 0=
 ; immediate
diff --git a/fth/t_corex.fth b/fth/t_corex.fth
index f2b3f19..c37252a 100644
--- a/fth/t_corex.fth
+++ b/fth/t_corex.fth
@@ -330,5 +330,19 @@ T{ s" unknown-query-string" ENVIRONMENT? }T{ FALSE }T
 T{ s" MAX-CHAR" ENVIRONMENT? }T{ 255 TRUE }T
 T{ s" ADDRESS-UNITS-BITS" ENVIRONMENT? }T{ 8 TRUE }T
 
+\  ----------------------------------------------------- PROGRAMMING
+
+T{ exists? words }T{ true }T  \ high level
+T{ exists? swap }T{ true }T   \ in kernel
+T{ exists? lkajsdlakjs }T{ false }T
+
+T{ [defined] if }T{ true }T   \ high level
+T{ [defined] dup }T{ true }T  \ in kernel
+T{ [defined] k23jh42 }T{ false }T
+
+T{ [undefined] if }T{ false }T  \ high level
+T{ [undefined] dup }T{ false }T \ in kernel
+T{ [undefined] k23jh42 }T{ true }T
+
 }TEST
 
-- 
2.30.2