cex: prefer → to ::=

It does not make a lot of sense to use ::= in our counterexamples,
that's not something that belongs to the Bison "vocabulary".  Using
the colon makes sense, but it's too discreet.  Let's use the arrow,
which we already use in some reports (HTML and Dot).

* src/gram.h (print_dot_fallback): Generalize into...
(print_fallback): this.
(print_arrow): New.
* src/derivation.c: Use it.

* NEWS, tests/conflicts.at, tests/counterexample.at,
* tests/diagnostics.at, tests/report.at: Adjust.
* doc/bison.texi: Ditto.
Unfortunately the literal `→` is output as `↦`.  So we need to use
@arrow.

1 files changed, 54 insertions, 54 deletions

diff --git a/tests/counterexample.at b/tests/counterexample.at
index 92ce5109..17123106 100644
--- a/tests/counterexample.at
+++ b/tests/counterexample.at
@@ -47,8 +47,8 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 [[input.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
 Shift/reduce conflict on token B:
   Example              A . B C
-  First derivation     s ::=[ a ::=[ A . ] x ::=[ B C ] ]
-  Second derivation    s ::=[ y ::=[ A . B ] c ::=[ C ] ]
+  First derivation     s -> [ a -> [ A . ] x -> [ B C ] ]
+  Second derivation    s -> [ y -> [ A . B ] c -> [ C ] ]
 
 input.y:4.4: warning: rule useless in parser due to conflicts [-Wother]
 ]])
@@ -76,13 +76,13 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 [[input.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
 Shift/reduce conflict on token B:
   Example              A . B C
-  First derivation     s ::=[ a ::=[ A . ] bc ::=[ B C ] ]
-  Second derivation    s ::=[ ac ::=[ A ac ::=[ b ::=[ . B ] ] C ] ]
+  First derivation     s -> [ a -> [ A . ] bc -> [ B C ] ]
+  Second derivation    s -> [ ac -> [ A ac -> [ b -> [ . B ] ] C ] ]
 
 Shift/reduce conflict on token B:
   Example              A A . B B C C
-  First derivation     s ::=[ a ::=[ A a ::=[ A . ] ] bc ::=[ B bc ::=[ B C ] C ] ]
-  Second derivation    s ::=[ ac ::=[ A ac ::=[ A ac ::=[ b ::=[ . b ::=[ B B ] ] ] C ] C ] ]
+  First derivation     s -> [ a -> [ A a -> [ A . ] ] bc -> [ B bc -> [ B C ] C ] ]
+  Second derivation    s -> [ ac -> [ A ac -> [ A ac -> [ b -> [ . b -> [ B B ] ] ] C ] C ] ]
 
 input.y:6.4: warning: rule useless in parser due to conflicts [-Wother]
 ]])
@@ -111,14 +111,14 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 [[input.y: warning: 2 shift/reduce conflicts [-Wconflicts-sr]
 Shift/reduce conflict on token B:
   Example              A . B
-  First derivation     s ::=[ ax ::=[ A x ::=[ . ] ] by ::=[ B y ::=[ ] ] ]
-  Second derivation    s ::=[ A xby ::=[ . B ] ]
+  First derivation     s -> [ ax -> [ A x -> [ . ] ] by -> [ B y -> [ ] ] ]
+  Second derivation    s -> [ A xby -> [ . B ] ]
 
 Shift/reduce conflict on token B:
   First example        A X . B y $end
-  First derivation     $accept ::=[ s ::=[ ax ::=[ A x ::=[ X x ::=[ . ] ] ] by ::=[ B y ] ] $end ]
+  First derivation     $accept -> [ s -> [ ax -> [ A x -> [ X x -> [ . ] ] ] by -> [ B y ] ] $end ]
   Second example       A X . B Y $end
-  Second derivation    $accept ::=[ s ::=[ A xby ::=[ X xby ::=[ . B ] Y ] ] $end ]
+  Second derivation    $accept -> [ s -> [ A xby -> [ X xby -> [ . B ] Y ] ] $end ]
 
 input.y:5.4-9: warning: rule useless in parser due to conflicts [-Wother]
 ]])
@@ -147,9 +147,9 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 [[input.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
 Shift/reduce conflict on token C:
   First example        B . C D $end
-  First derivation     $accept ::=[ g ::=[ x ::=[ b ::=[ B . ] cd ::=[ C D ] ] ] $end ]
+  First derivation     $accept -> [ g -> [ x -> [ b -> [ B . ] cd -> [ C D ] ] ] $end ]
   Second example       B . C $end
-  Second derivation    $accept ::=[ g ::=[ x ::=[ bc ::=[ B . C ] ] ] $end ]
+  Second derivation    $accept -> [ g -> [ x -> [ bc -> [ B . C ] ] ] $end ]
 
 input.y:6.4: warning: rule useless in parser due to conflicts [-Wother]
 ]])
@@ -176,9 +176,9 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 [[input.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
 Shift/reduce conflict on token A:
   First example        A . A $end
-  First derivation     $accept ::=[ s ::=[ s ::=[ t ::=[ x ::=[ A . ] ] ] t ::=[ x ::=[ A ] ] ] $end ]
+  First derivation     $accept -> [ s -> [ s -> [ t -> [ x -> [ A . ] ] ] t -> [ x -> [ A ] ] ] $end ]
   Second example       A . A B $end
-  Second derivation    $accept ::=[ s ::=[ t ::=[ y ::=[ A . A B ] ] ] $end ]
+  Second derivation    $accept -> [ s -> [ t -> [ y -> [ A . A B ] ] ] $end ]
 
 ]])
 
@@ -209,14 +209,14 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 [[input.y: warning: 2 shift/reduce conflicts [-Wconflicts-sr]
 Shift/reduce conflict on token A:
   Example              b . A X X Y
-  First derivation     a ::=[ r ::=[ b . ] t ::=[ A x ::=[ X ] xy ::=[ X Y ] ] ]
-  Second derivation    a ::=[ s ::=[ b . xx ::=[ A X X ] y ::=[ Y ] ] ]
+  First derivation     a -> [ r -> [ b . ] t -> [ A x -> [ X ] xy -> [ X Y ] ] ]
+  Second derivation    a -> [ s -> [ b . xx -> [ A X X ] y -> [ Y ] ] ]
 
 Shift/reduce conflict on token X:
   First example        X . X xy
-  First derivation     a ::=[ x ::=[ X . ] t ::=[ X xy ] ]
+  First derivation     a -> [ x -> [ X . ] t -> [ X xy ] ]
   Second example       A X . X
-  Second derivation    a ::=[ t ::=[ A xx ::=[ X . X ] ] ]
+  Second derivation    a -> [ t -> [ A xx -> [ X . X ] ] ]
 
 input.y:4.4: warning: rule useless in parser due to conflicts [-Wother]
 input.y:8.4: warning: rule useless in parser due to conflicts [-Wother]
@@ -242,8 +242,8 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 [[input.y: warning: 1 reduce/reduce conflict [-Wconflicts-rr]
 Reduce/reduce conflict on token $end:
   Example              A b .
-  First derivation     a ::=[ A b . ]
-  Second derivation    a ::=[ A b ::=[ b . ] ]
+  First derivation     a -> [ A b . ]
+  Second derivation    a -> [ A b -> [ b . ] ]
 
 input.y:4.9: warning: rule useless in parser due to conflicts [-Wother]
 ]])
@@ -269,9 +269,9 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 [[input.y: warning: 2 reduce/reduce conflicts [-Wconflicts-rr]
 Reduce/reduce conflict on tokens A, C:
   First example        D . A $end
-  First derivation     $accept ::=[ s ::=[ a ::=[ D . ] A ] $end ]
+  First derivation     $accept -> [ s -> [ a -> [ D . ] A ] $end ]
   Second example       B D . A $end
-  Second derivation    $accept ::=[ s ::=[ B b ::=[ D . ] A ] $end ]
+  Second derivation    $accept -> [ s -> [ B b -> [ D . ] A ] $end ]
 
 input.y:5.4: warning: rule useless in parser due to conflicts [-Wother]
 ]])
@@ -298,9 +298,9 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 Shift/reduce conflict on token J:
 time limit exceeded: XXX
   First example        H i . J $end
-  First derivation     $accept ::=[ s ::=[ a ::=[ H i . ] J ] $end ]
+  First derivation     $accept -> [ s -> [ a -> [ H i . ] J ] $end ]
   Second example       H i . J K $end
-  Second derivation    $accept ::=[ a ::=[ H i ::=[ i . J K ] ] $end ]
+  Second derivation    $accept -> [ a -> [ H i -> [ i . J K ] ] $end ]
 
 input.y:4.4-6: warning: rule useless in parser due to conflicts [-Wother]
 ]])
@@ -330,13 +330,13 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 [[input.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
 Shift/reduce conflict on token B:
   Example              N A . B C
-  First derivation     s ::=[ n ::=[ N a ::=[ A . ] B ] C ]
-  Second derivation    s ::=[ n ::=[ N b ::=[ A . B C ] ] ]
+  First derivation     s -> [ n -> [ N a -> [ A . ] B ] C ]
+  Second derivation    s -> [ n -> [ N b -> [ A . B C ] ] ]
 
 Shift/reduce conflict on token B:
   Example              N N A . B D C
-  First derivation     s ::=[ n ::=[ N n ::=[ N a ::=[ A . ] B ] D ] C ]
-  Second derivation    s ::=[ n ::=[ N n ::=[ N b ::=[ A . B D ] ] C ] ]
+  First derivation     s -> [ n -> [ N n -> [ N a -> [ A . ] B ] D ] C ]
+  Second derivation    s -> [ n -> [ N n -> [ N b -> [ A . B D ] ] C ] ]
 
 input.y:5.4: warning: rule useless in parser due to conflicts [-Wother]
 ]])
@@ -367,13 +367,13 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 [[input.y: warning: 4 reduce/reduce conflicts [-Wconflicts-rr]
 Reduce/reduce conflict on tokens b, c:
   Example              B . b c
-  First derivation     S ::=[ B ::=[ A ::=[ B . ] b A ::=[ ] ] C ::=[ A ::=[ ] c A ::=[ ] ] ]
-  Second derivation    S ::=[ B C ::=[ A ::=[ B ::=[ A ::=[ . ] b A ::=[ ] ] ] c A ::=[ ] ] ]
+  First derivation     S -> [ B -> [ A -> [ B . ] b A -> [ ] ] C -> [ A -> [ ] c A -> [ ] ] ]
+  Second derivation    S -> [ B C -> [ A -> [ B -> [ A -> [ . ] b A -> [ ] ] ] c A -> [ ] ] ]
 
 Reduce/reduce conflict on tokens b, c:
   Example              C . c b
-  First derivation     S ::=[ C ::=[ A ::=[ C . ] c A ::=[ ] ] B ::=[ A ::=[ ] b A ::=[ ] ] ]
-  Second derivation    S ::=[ C B ::=[ A ::=[ C ::=[ A ::=[ . ] c A ::=[ ] ] ] b A ::=[ ] ] ]
+  First derivation     S -> [ C -> [ A -> [ C . ] c A -> [ ] ] B -> [ A -> [ ] b A -> [ ] ] ]
+  Second derivation    S -> [ C B -> [ A -> [ C -> [ A -> [ . ] c A -> [ ] ] ] b A -> [ ] ] ]
 
 ]])
 
@@ -400,52 +400,52 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 input.y: warning: 6 reduce/reduce conflicts [-Wconflicts-rr]
 Reduce/reduce conflict on token A:
   First example        . c A A $end
-  First derivation     $accept ::=[ a ::=[ b ::=[ . ] d ::=[ c A A ] ] $end ]
+  First derivation     $accept -> [ a -> [ b -> [ . ] d -> [ c A A ] ] $end ]
   Second example       . c A A $end
-  Second derivation    $accept ::=[ a ::=[ c ::=[ . ] d ::=[ c A A ] ] $end ]
+  Second derivation    $accept -> [ a -> [ c -> [ . ] d -> [ c A A ] ] $end ]
 
 Reduce/reduce conflict on token A:
 time limit exceeded: XXX
   First example        b . c A A $end
-  First derivation     $accept ::=[ a ::=[ b d ::=[ a ::=[ b ::=[ . ] d ::=[ c A A ] ] ] ] $end ]
+  First derivation     $accept -> [ a -> [ b d -> [ a -> [ b -> [ . ] d -> [ c A A ] ] ] ] $end ]
   Second example       b . A $end
-  Second derivation    $accept ::=[ a ::=[ b d ::=[ c ::=[ . ] A ] ] $end ]
+  Second derivation    $accept -> [ a -> [ b d -> [ c -> [ . ] A ] ] $end ]
 
 Reduce/reduce conflict on token A:
 time limit exceeded: XXX
   First example        c . c A A $end
-  First derivation     $accept ::=[ a ::=[ c d ::=[ a ::=[ b ::=[ . ] d ::=[ c A A ] ] ] ] $end ]
+  First derivation     $accept -> [ a -> [ c d -> [ a -> [ b -> [ . ] d -> [ c A A ] ] ] ] $end ]
   Second example       c . A $end
-  Second derivation    $accept ::=[ a ::=[ c d ::=[ c ::=[ . ] A ] ] $end ]
+  Second derivation    $accept -> [ a -> [ c d -> [ c -> [ . ] A ] ] $end ]
 
 Shift/reduce conflict on token A:
 time limit exceeded: XXX
   First example        b c . c A A $end
-  First derivation     $accept ::=[ a ::=[ b d ::=[ a ::=[ c d ::=[ a ::=[ b ::=[ . ] d ::=[ c A A ] ] ] ] ] ] $end ]
+  First derivation     $accept -> [ a -> [ b d -> [ a -> [ c d -> [ a -> [ b -> [ . ] d -> [ c A A ] ] ] ] ] ] $end ]
   Second example       b c . A
-  Second derivation    a ::=[ b d ::=[ c . A ] ]
+  Second derivation    a -> [ b d -> [ c . A ] ]
 
 Reduce/reduce conflict on token A:
   First example        b c . c A A $end
-  First derivation     $accept ::=[ a ::=[ b d ::=[ a ::=[ c d ::=[ a ::=[ b ::=[ . ] d ::=[ c A A ] ] ] ] ] ] $end ]
+  First derivation     $accept -> [ a -> [ b d -> [ a -> [ c d -> [ a -> [ b -> [ . ] d -> [ c A A ] ] ] ] ] ] $end ]
   Second example       b c . A $end
-  Second derivation    $accept ::=[ a ::=[ b d ::=[ a ::=[ c d ::=[ c ::=[ . ] A ] ] ] ] $end ]
+  Second derivation    $accept -> [ a -> [ b d -> [ a -> [ c d -> [ c -> [ . ] A ] ] ] ] $end ]
 
 Shift/reduce conflict on token A:
   First example        b c . A $end
-  First derivation     $accept ::=[ a ::=[ b d ::=[ a ::=[ c d ::=[ c ::=[ . ] A ] ] ] ] $end ]
+  First derivation     $accept -> [ a -> [ b d -> [ a -> [ c d -> [ c -> [ . ] A ] ] ] ] $end ]
   Second example       b c . A
-  Second derivation    a ::=[ b d ::=[ c . A ] ]
+  Second derivation    a -> [ b d -> [ c . A ] ]
 
 Reduce/reduce conflict on token $end:
   Example              b d .
-  First derivation     a ::=[ b d . ]
-  Second derivation    a ::=[ b d ::=[ d . ] ]
+  First derivation     a -> [ b d . ]
+  Second derivation    a -> [ b d -> [ d . ] ]
 
 Reduce/reduce conflict on token $end:
   Example              c d .
-  First derivation     a ::=[ c d . ]
-  Second derivation    a ::=[ c d ::=[ d . ] ]
+  First derivation     a -> [ c d . ]
+  Second derivation    a -> [ c d -> [ d . ] ]
 
 input.y:5.4: warning: rule useless in parser due to conflicts [-Wother]
 input.y:6.15: warning: rule useless in parser due to conflicts [-Wother]
@@ -475,8 +475,8 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 [[input.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
 Shift/reduce conflict on token J:
   Example              H i J . J J
-  First derivation     s ::=[ a ::=[ H i ::=[ i J . ] J J ] ]
-  Second derivation    s ::=[ a ::=[ H i J . J ] J ]
+  First derivation     s -> [ a -> [ H i -> [ i J . ] J J ] ]
+  Second derivation    s -> [ a -> [ H i J . J ] J ]
 
 input.y:5.13-15: warning: rule useless in parser due to conflicts [-Wother]
 ]])
@@ -507,8 +507,8 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 [[input.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
 Shift/reduce conflict on token D:
   Example              A a . D
-  First derivation     s ::=[ A a a ::=[ b ::=[ c ::=[ . ] ] ] d ::=[ D ] ]
-  Second derivation    s ::=[ A a d ::=[ . D ] ]
+  First derivation     s -> [ A a a -> [ b -> [ c -> [ . ] ] ] d -> [ D ] ]
+  Second derivation    s -> [ A a d -> [ . D ] ]
 
 ]])
 
@@ -537,9 +537,9 @@ AT_BISON_CHECK_CEX([input.y], [], [],
 [[input.y: warning: 1 shift/reduce conflict [-Wconflicts-sr]
 Shift/reduce conflict on token D:
   First example        A a . D E $end
-  First derivation     $accept ::=[ s ::=[ A a a ::=[ b ::=[ c ::=[ . ] ] ] d ::=[ D ] E ] $end ]
+  First derivation     $accept -> [ s -> [ A a a -> [ b -> [ c -> [ . ] ] ] d -> [ D ] E ] $end ]
   Second example       A a . D $end
-  Second derivation    $accept ::=[ s ::=[ A a d ::=[ . D ] ] $end ]
+  Second derivation    $accept -> [ s -> [ A a d -> [ . D ] ] $end ]
 
 ]])