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(Location Default Action): Don't claim that

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we have an array of locations.  Use the same macro for both glr
and lalr parsers.  Mention YYRHSLOC.  Mention what happens when
the index is 0.
This commit is contained in:
Paul Eggert
2004-12-12 09:24:56 +00:00
parent a4e1a53bf9
commit 766de5eb7c
1 changed files with 29 additions and 25 deletions
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doc/bison.texinfo
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@@ -3446,38 +3446,40 @@ dedicated code from semantic actions.
The @code{YYLLOC_DEFAULT} macro takes three parameters. The first one is
the location of the grouping (the result of the computation). When a
rule is matched, the second parameter is an array holding locations of
rule is matched, the second parameter identifies locations of
all right hand side elements of the rule being matched, and the third
parameter is the size of the rule's right hand side. When processing
a syntax error, the second parameter is an array holding locations of
a syntax error, the second parameter identifies locations of
the symbols that were discarded during error processing, and the third
parameter is the number of discarded symbols.
By default, @code{YYLLOC_DEFAULT} is defined this way for simple
@acronym{LALR}(1) parsers:
By default, @code{YYLLOC_DEFAULT} is defined this way:
@example
@smallexample
@group
# define YYLLOC_DEFAULT(Current, Rhs, N) \
((Current).first_line = (Rhs)[1].first_line, \
(Current).first_column = (Rhs)[1].first_column, \
(Current).last_line = (Rhs)[N].last_line, \
(Current).last_column = (Rhs)[N].last_column)
# define YYLLOC_DEFAULT(Current, Rhs, N) \
do \
if (N) \
@{ \
(Current).first_line = YYRHSLOC(Rhs, 1).first_line; \
(Current).first_column = YYRHSLOC(Rhs, 1).first_column; \
(Current).last_line = YYRHSLOC(Rhs, N).last_line; \
(Current).last_column = YYRHSLOC(Rhs, N).last_column; \
@} \
else \
@{ \
(Current).first_line = (Current).last_line = \
YYRHSLOC(Rhs, 0).last_line; \
(Current).first_column = (Current).last_column = \
YYRHSLOC(Rhs, 0).last_column; \
@} \
while (0)
@end group
@end example
@end smallexample
@noindent
and like this for @acronym{GLR} parsers:
@example
@group
# define YYLLOC_DEFAULT(yyCurrent, yyRhs, YYN) \
((yyCurrent).first_line = YYRHSLOC(yyRhs, 1).first_line, \
(yyCurrent).first_column = YYRHSLOC(yyRhs, 1).first_column, \
(yyCurrent).last_line = YYRHSLOC(yyRhs, YYN).last_line, \
(yyCurrent).last_column = YYRHSLOC(yyRhs, YYN).last_column)
@end group
@end example
where @code{YYRHSLOC (rhs, k)} is the location of the @var{k}th symbol
in @var{rhs} when @var{k} is positive, and the location of the symbol
just before the reduction when @var{k} is zero.
When defining @code{YYLLOC_DEFAULT}, you should consider that:
@@ -3487,8 +3489,10 @@ All arguments are free of side-effects. However, only the first one (the
result) should be modified by @code{YYLLOC_DEFAULT}.
@item
For consistency with semantic actions, valid indexes for the location
array range from 1 to @var{n}.
For consistency with semantic actions, valid indexes within the
right hand side range from 1 to @var{n}. When @var{n} is zero, only 0 is a
valid index, and it refers to the symbol just before the reduction.
During error processing @var{n} is always positive.
@item
Your macro should parenthesize its arguments, if need be, since the