initiate error recovery.
During deterministic GLR operation, the effect of @code{YYERROR} is
the same as its effect in a deterministic parser.
-The effect in a deferred action is similar, but the precise point of the
-error is undefined; instead, the parser reverts to deterministic operation,
+The effect in a deferred action is similar, but the precise point of the
+error is undefined; instead, the parser reverts to deterministic operation,
selecting an unspecified stack on which to continue with a syntax error.
In a semantic predicate (see @ref{Semantic Predicates}) during nondeterministic
parsing, @code{YYERROR} silently prunes
@end smallexample
@noindent
-is one way to allow the same parser to handle two different syntaxes for
+is one way to allow the same parser to handle two different syntaxes for
widgets. The clause preceded by @code{%?} is treated like an ordinary
action, except that its text is treated as an expression and is always
-evaluated immediately (even when in nondeterministic mode). If the
+evaluated immediately (even when in nondeterministic mode). If the
expression yields 0 (false), the clause is treated as a syntax error,
-which, in a nondeterministic parser, causes the stack in which it is reduced
+which, in a nondeterministic parser, causes the stack in which it is reduced
to die. In a deterministic parser, it acts like YYERROR.
As the example shows, predicates otherwise look like semantic actions, and
There is a subtle difference between semantic predicates and ordinary
actions in nondeterministic mode, since the latter are deferred.
-For example, we could try to rewrite the previous example as
+For example, we could try to rewrite the previous example as
@smallexample
widget :
false). However, this
does @emph{not} have the same effect if @code{new_args} and @code{old_args}
have overlapping syntax.
-Since the mid-rule actions testing @code{new_syntax} are deferred,
+Since the mid-rule actions testing @code{new_syntax} are deferred,
a GLR parser first encounters the unresolved ambiguous reduction
for cases where @code{new_args} and @code{old_args} recognize the same string
@emph{before} performing the tests of @code{new_syntax}. It therefore
Do not allow @code{YYINITDEPTH} to be greater than @code{YYMAXDEPTH}.
You can generate a deterministic parser containing C++ user code from
-the default (C) skeleton, as well as from the C++ skeleton
+the default (C) skeleton, as well as from the C++ skeleton
(@pxref{C++ Parsers}). However, if you do use the default skeleton
and want to allow the parsing stack to grow,
be careful not to use semantic types or location types that require
@defcv {Type} {parser} {syntax_error}
This class derives from @code{std::runtime_error}. Throw instances of it
-from user actions to raise parse errors. This is equivalent with first
+from the scanner or from the user actions to raise parse errors. This is
+equivalent with first
invoking @code{error} to report the location and message of the syntax
error, and then to invoke @code{YYERROR} to enter the error-recovery mode.
But contrary to @code{YYERROR} which can only be invoked from user actions
send additional files as well (such as `config.h' or `config.cache').
Patches are most welcome, but not required. That is, do not hesitate to
-send a bug report just because you can not provide a fix.
+send a bug report just because you cannot provide a fix.
Send bug reports to @email{bug-bison@@gnu.org}.
projects / bison.git / blobdiff