Lines Matching refs:ahead
251 * Look-Ahead:: Parser looks one token ahead when deciding what to do.
448 token of look-ahead. Strictly speaking, that is a description of an
464 (called a @dfn{look-ahead}) of the remaining input. A context-free
468 look-ahead always suffices to determine the next grammar rule to apply.
749 Such grammars typically require more than one symbol of look-ahead,
789 With normal @acronym{LALR}(1) one-token look-ahead it is not
828 look-ahead than the underlying @acronym{LALR}(1) algorithm actually allows
1109 the look-ahead token present at the time of the associated reduction.
1112 look-ahead token's semantic value and location, if any.
3192 It is also possible to access the semantic value of the look-ahead token, if
3380 the @dfn{look-ahead} token at this time, since the parser is still
3554 It is also possible to access the location of the look-ahead token, if any,
3902 @code{@@$} --- initial value and location of the look-ahead --- and the
3974 the current look-ahead and the entire stack (except the current
4312 parser states and what is done for each type of look-ahead token in
4860 a single value, and only when there is no look-ahead token.
4862 It installs a look-ahead token with token type @var{token} and
4867 a look-ahead token already, then it reports a syntax error with
4876 Value stored in @code{yychar} when there is no look-ahead token.
4881 Value stored in @code{yychar} when the look-ahead is the end of the input
4902 Variable containing either the look-ahead token, or @code{YYEOF} when the
4903 look-ahead is the end of the input stream, or @code{YYEMPTY} when no look-ahead
4911 Discard the current look-ahead token. This is useful primarily in
4925 Variable containing the look-ahead token location when @code{yychar} is not set
4933 Variable containing the look-ahead token semantic value when @code{yychar} is
5114 * Look-Ahead:: Parser looks one token ahead when deciding what to do.
5127 @cindex look-ahead token
5132 reduction is possible, the parser sometimes ``looks ahead'' at the next
5136 @dfn{look-ahead token}, which is not on the stack. Now the parser can
5138 the look-ahead token remains off to the side. When no more reductions
5139 should take place, the look-ahead token is shifted onto the stack. This
5141 token type of the look-ahead token, some rules may choose to delay their
5144 Here is a simple case where look-ahead is needed. These three rules define
5179 The look-ahead token is stored in the variable @code{yychar}.
5207 When the @code{ELSE} token is read and becomes the look-ahead token, the
5341 contains @w{@samp{1 - 2}} and the look-ahead token is @samp{-}: shifting
5402 of the rule being considered with that of the look-ahead token. If the
5411 the look-ahead token has no precedence, then the default is to shift.
5505 Each time a look-ahead token is read, the current parser state together
5506 with the type of look-ahead token are looked up in a table. This table
5507 entry can say, ``Shift the look-ahead token.'' In this case, it also
5515 There is one other alternative: the table can say that the look-ahead token
5673 of look-ahead: when a @code{param_spec} is being read, an @code{ID} is
5687 that the rules would require different look-ahead tokens in the two
5760 based on a summary of the preceding input and on one extra token of look-ahead.
5766 look-ahead, since the parser lacks the information necessary to make a
5943 look-ahead token is not acceptable to be shifted next, the parser reads
5994 The previous look-ahead token is reanalyzed immediately after an error. If
6003 probably correct. The previous look-ahead token ought to be discarded
6391 symbol, and the look-ahead is a @code{NUM}, then this token is shifted on
6393 look-ahead triggers a syntax error.''
6400 report lists @code{NUM} as a look-ahead token because @code{NUM} can be
6434 the rule 5, @samp{exp: NUM;}, is completed. Whatever the look-ahead token
6457 because of the item @samp{exp -> exp . '+' exp}, if the look-ahead if
6534 Indeed, there are two actions associated to the look-ahead @samp{/}:
6552 possible, the look-ahead is required to select the action. State 8 is
6553 one such state: if the look-ahead is @samp{*} or @samp{/} then the action
6556 look-ahead token is @samp{*}, since we specified that @samp{*} has higher
6558 with some set of possible look-ahead tokens. When run with
6559 @option{--report=look-ahead}, Bison specifies these look-ahead tokens:
6917 @item look-ahead
6919 each rule's look-ahead set.
8210 token @code{error} becomes the current look-ahead token. Actions
8211 corresponding to @code{error} are then executed, and the look-ahead
8351 Macro to discard a value from the parser stack and fake a look-ahead
8357 look-ahead token. (In a pure parser, it is a local variable within
8364 look-ahead token. @xref{Error Recovery}.
8430 In semantic actions, it stores the location of the look-ahead token.
8445 In semantic actions, it stores the semantic value of the look-ahead token.
8585 @item Look-ahead token
8596 look-ahead is needed to disambiguate the parsing of any piece of input.