From: Mark Thom <markjordanthom@gmail.com>
Date: Tue, 14 Jan 2020 03:30:58 +0000 (-0700)
Subject: add simple gensym library
X-Git-Tag: v0.8.118~26
X-Git-Url: https://git.sagredo.dev/?a=commitdiff_plain;h=728be8c259b61b0e66d3ba5ade925cb88cbff7c4;p=scryer-prolog.git

add simple gensym library
---

diff --git a/src/prolog/lib/gensym.pl b/src/prolog/lib/gensym.pl
new file mode 100644
index 00000000..7b0f6cb5
--- /dev/null
+++ b/src/prolog/lib/gensym.pl
@@ -0,0 +1,29 @@
+
+:- module(gensym, [gensym/2,
+		   reset_gensym/1]).
+
+:- use_module(library(error)).
+:- use_module(library(lists)).
+:- use_module(library(non_iso)).
+:- use_module(library(si)).
+
+append_id(Base, UniqueID, Unique) :-
+    atom_chars(Base, BaseChars),
+    number_chars(UniqueID, IDChars),
+    append(BaseChars, IDChars, AtomChars),
+    atom_chars(Unique, AtomChars).
+
+gensym(Base, Unique) :-
+    must_be(var, Unique),
+    atom_si(Base),    
+    (  bb_get(Base, UniqueID0) ->
+       UniqueID is UniqueID0 + 1,
+       bb_put(Base, UniqueID),
+       append_id(Base, UniqueID, Unique)
+    ;  bb_put(Base, 1),
+       append_id(Base, 1, Unique)
+    ).
+
+reset_gensym(Base) :-
+    atom_si(Base),
+    bb_put(Base, 0).