From 2e1f598aa2e0a2adfec3cb72a8d09d6e0a94174a Mon Sep 17 00:00:00 2001
From: Simon Forman <sforman@hushmail.com>
Date: Sun, 11 Aug 2019 21:30:02 -0700
Subject: [PATCH] Experiment with putting logic vars on the stack.

---
 thun/gnu-prolog/defs.pl   | 1 +
 thun/gnu-prolog/defs.txt  | 1 +
 thun/gnu-prolog/parser.pl | 6 ++++--
 thun/gnu-prolog/thun.pl   | 1 +
 4 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/thun/gnu-prolog/defs.pl b/thun/gnu-prolog/defs.pl
index 4ad0bb6..43851e2 100644
--- a/thun/gnu-prolog/defs.pl
+++ b/thun/gnu-prolog/defs.pl
@@ -28,6 +28,7 @@ def(grba,[[stack,popd],dip]).
 def(hypot,[[sqr],ii,+,sqrt]).
 def(ifte,[[nullary],dipd,swap,branch]).
 def(ii,[[dip],dupdip,i]).
+def(infer,[thunk,dup,rollup,infra]).
 def(infra,[swons,swaack,[i],dip,swaack]).
 def(infrst,[infra,first]).
 def(least_fraction,[dup,[gcd],infra,[div],concat,map]).
diff --git a/thun/gnu-prolog/defs.txt b/thun/gnu-prolog/defs.txt
index f31f284..7be86c2 100644
--- a/thun/gnu-prolog/defs.txt
+++ b/thun/gnu-prolog/defs.txt
@@ -30,6 +30,7 @@ grba == [stack popd] dip
 hypot == [sqr] ii + sqrt
 ifte == [nullary] dipd swap branch
 ii == [dip] dupdip i
+infer == thunk dup rollup infra
 infra == swons swaack [i] dip swaack
 infrst == infra first
 least_fraction == dup [gcd] infra [div] concat map
diff --git a/thun/gnu-prolog/parser.pl b/thun/gnu-prolog/parser.pl
index ab43ac7..fadd6c9 100644
--- a/thun/gnu-prolog/parser.pl
+++ b/thun/gnu-prolog/parser.pl
@@ -100,8 +100,10 @@ format_joy([T])   --> format_term(T), !.
 format_joy([T|S]) --> format_term(T), " ", format_joy(S).
 format_joy([])    --> [].
 
-format_term(N) --> {number(N), number_codes(N, Codes)}, Codes.
-format_term(A) --> {  atom(A),   atom_codes(A, Codes)}, Codes.
+format_term(N) --> {number(N),   number_codes(N, Codes)}, Codes.
+format_term(A) --> {  atom(A),     atom_codes(A, Codes)}, Codes.
+format_term(V) --> {   var(V), write_to_codes(Codes, V)}, Codes.
 format_term([A|As]) --> "[", format_joy([A|As]), "]".
+format_term(F) --> {    write_to_codes(Codes, F)}, Codes.
 
 
diff --git a/thun/gnu-prolog/thun.pl b/thun/gnu-prolog/thun.pl
index 3eb8a97..b3651b6 100644
--- a/thun/gnu-prolog/thun.pl
+++ b/thun/gnu-prolog/thun.pl
@@ -91,6 +91,7 @@ func(clear,        _ ,      []).
 func(first, [[X|_]|S],   [X|S]).
 func(rest,  [[_|X]|S],   [X|S]).
 func(unit,      [X|S], [[X]|S]).
+func(thunk,        S ,   [X|S]).
 
 func(rolldown, [A, B, C|S], [B, C, A|S]).
 func(dupd,        [A, B|S], [A, B, B|S]).