From 28065b0565ec9ec50b8802e5eddf7575533182a3 Mon Sep 17 00:00:00 2001
From: Markus Triska <triska@metalevel.at>
Date: Fri, 30 Jun 2023 18:01:17 +0200
Subject: [PATCH 1/4] constrain bracketing to operators with pertaining arity

Example:

    ?- X = -->(a,b,c).
       X = -->(a,b,c).
---
 src/toplevel.pl | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/toplevel.pl b/src/toplevel.pl
index ff463833..d61e324f 100644
--- a/src/toplevel.pl
+++ b/src/toplevel.pl
@@ -208,8 +208,9 @@ needs_bracketing(Value, Op) :-
     nonvar(Value),
     \+ integer(Value),
     functor(Value, F, Arity),
-    current_op(FPrec, _, F),
+    current_op(FPrec, FSpec, F),
     current_op(EqPrec, EqSpec, Op),
+    arity_specifier(Arity, FSpec),
     (  Arity =:= 0 ->
        true
     ;  EqPrec < FPrec ->
@@ -222,6 +223,10 @@ needs_bracketing(Value, Op) :-
        memberchk(EqSpec, [fx,xfx,yfx])
     ).
 
+arity_specifier(0, _).
+arity_specifier(1, S) :- atom_chars(S, [_,_]).
+arity_specifier(2, S) :- atom_chars(S, [_,_,_]).
+
 write_goal(G, VarList, MaxDepth) :-
     (  G = (Var = Value) ->
        (  var(Value) ->

From bfe808a779252d98e23db1e5d4e0fa01a31ac625 Mon Sep 17 00:00:00 2001
From: Markus Triska <triska@metalevel.at>
Date: Fri, 30 Jun 2023 18:01:54 +0200
Subject: [PATCH 2/4] shorten needs_bracketing/2

---
 src/toplevel.pl | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/src/toplevel.pl b/src/toplevel.pl
index d61e324f..7d1e2569 100644
--- a/src/toplevel.pl
+++ b/src/toplevel.pl
@@ -211,16 +211,12 @@ needs_bracketing(Value, Op) :-
     current_op(FPrec, FSpec, F),
     current_op(EqPrec, EqSpec, Op),
     arity_specifier(Arity, FSpec),
-    (  Arity =:= 0 ->
-       true
-    ;  EqPrec < FPrec ->
-       true
-    ;  FPrec > 0, F == Value, graphic_token_char(F) ->
-       true
-    ;  F \== '.', '$quoted_token'(F) ->
-       true
-    ;  EqPrec == FPrec,
-       memberchk(EqSpec, [fx,xfx,yfx])
+    (  Arity =:= 0
+    ;  EqPrec < FPrec
+    ;  FPrec > 0, F == Value, graphic_token_char(F)
+    ;  F \== '.', '$quoted_token'(F)
+    ;  EqPrec =:= FPrec,
+       member(EqSpec, [fx,xfx,yfx])
     ).
 
 arity_specifier(0, _).

From a3f8ddd24a786e44d9c7183bb724e6d536d2bc9b Mon Sep 17 00:00:00 2001
From: Markus Triska <triska@metalevel.at>
Date: Fri, 30 Jun 2023 18:02:43 +0200
Subject: [PATCH 3/4] remove subsumed case: F == Value means Arity =:= 0, now
 considered above

---
 src/toplevel.pl | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/toplevel.pl b/src/toplevel.pl
index 7d1e2569..8a0d44ea 100644
--- a/src/toplevel.pl
+++ b/src/toplevel.pl
@@ -213,7 +213,6 @@ needs_bracketing(Value, Op) :-
     arity_specifier(Arity, FSpec),
     (  Arity =:= 0
     ;  EqPrec < FPrec
-    ;  FPrec > 0, F == Value, graphic_token_char(F)
     ;  F \== '.', '$quoted_token'(F)
     ;  EqPrec =:= FPrec,
        member(EqSpec, [fx,xfx,yfx])

From 42282c6e6ec0cff6fc110b0a6be23addc4b11088 Mon Sep 17 00:00:00 2001
From: Markus Triska <triska@metalevel.at>
Date: Fri, 30 Jun 2023 18:03:21 +0200
Subject: [PATCH 4/4] remove unneeded case: only operator definitions should
 count, not quoting

---
 src/toplevel.pl | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/toplevel.pl b/src/toplevel.pl
index 8a0d44ea..2cfe04f5 100644
--- a/src/toplevel.pl
+++ b/src/toplevel.pl
@@ -213,7 +213,6 @@ needs_bracketing(Value, Op) :-
     arity_specifier(Arity, FSpec),
     (  Arity =:= 0
     ;  EqPrec < FPrec
-    ;  F \== '.', '$quoted_token'(F)
     ;  EqPrec =:= FPrec,
        member(EqSpec, [fx,xfx,yfx])
     ).