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Add %precedence support.

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Unfortunately it is not possible to reuse the %prec directive.  This
is because to please POSIX, we do not require to end the rules with a
semicolon.  As a result,

foo: bar %prec baz

is ambiguous: either a rule which precedence is that of baz, or a rule,
and then a declaration of the precedence of the token baz.

	* doc/bison.texinfo: Document %precedence.
	(Precedence Only): New.
	* src/assoc.h, src/assoc.c (precedence_assoc): New.
	* src/conflicts.c (resolve_sr_conflict): Support it.
	* src/scan-gram.l, src/parse-gram.y (%precedence): New token.
	Parse it.
	* tests/calc.at: Use %precedence for NEG.
	* tests/conflicts.at (%precedence does not suffice)
	(%precedence suffices): New tests.
This commit is contained in:
Akim Demaille
2008-08-07 23:15:34 +02:00
parent c85be41a07
commit d78f0ac9d8
9 changed files with 195 additions and 40 deletions
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8
src/parse-gram.y
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@@ -115,6 +115,7 @@ static int current_prec = 0;
%token PERCENT_LEFT "%left"
%token PERCENT_RIGHT "%right"
%token PERCENT_NONASSOC "%nonassoc"
%token PERCENT_PRECEDENCE "%precedence"
%token PERCENT_PREC "%prec"
%token PERCENT_DPREC "%dprec"
@@ -412,9 +413,10 @@ precedence_declaration:
;
precedence_declarator:
"%left" { $$ = left_assoc; }
| "%right" { $$ = right_assoc; }
| "%nonassoc" { $$ = non_assoc; }
"%left" { $$ = left_assoc; }
| "%right" { $$ = right_assoc; }
| "%nonassoc" { $$ = non_assoc; }
| "%precedence" { $$ = precedence_assoc; }
;
type.opt: