* C++ Scanner Interface:: Exchanges between yylex and parse
* A Complete C++ Example:: Demonstrating their use
+C++ Location Values
+
+* C++ position:: One point in the source file
+* C++ location:: Two points in the source file
+
A Complete C++ Example
* Calc++ --- C++ Calculator:: The specifications
parse. Finally, the base of the temporary stack used during an exploratory
parse is a pointer into the normal parser state stack so that the stack is
never physically copied. In our experience, the performance penalty of LAC
-has proven insignificant for practical grammars.
+has proved insignificant for practical grammars.
@end itemize
While the LAC algorithm shares techniques that have been recognized in the
order of the output and the exact presentation might vary, but the
interpretation is the same.
-The first section includes details on conflicts that were solved thanks
-to precedence and/or associativity:
-
-@example
-Conflict in state 8 between rule 2 and token '+' resolved as reduce.
-Conflict in state 8 between rule 2 and token '-' resolved as reduce.
-Conflict in state 8 between rule 2 and token '*' resolved as shift.
-@exdent @dots{}
-@end example
-
-@noindent
-The next section lists states that still have conflicts.
-
-@example
-State 8 conflicts: 1 shift/reduce
-State 9 conflicts: 1 shift/reduce
-State 10 conflicts: 1 shift/reduce
-State 11 conflicts: 4 shift/reduce
-@end example
-
@noindent
@cindex token, useless
@cindex useless token
@cindex useless nonterminal
@cindex rule, useless
@cindex useless rule
-The next section reports useless tokens, nonterminal and rules. Useless
-nonterminals and rules are removed in order to produce a smaller parser,
-but useless tokens are preserved, since they might be used by the
-scanner (note the difference between ``useless'' and ``unused''
-below):
+The first section reports useless tokens, nonterminals and rules. Useless
+nonterminals and rules are removed in order to produce a smaller parser, but
+useless tokens are preserved, since they might be used by the scanner (note
+the difference between ``useless'' and ``unused'' below):
@example
-Nonterminals useless in grammar:
+Nonterminals useless in grammar
useless
-Terminals unused in grammar:
+Terminals unused in grammar
STR
-Rules useless in grammar:
-#6 useless: STR;
+Rules useless in grammar
+ 6 useless: STR
+@end example
+
+@noindent
+The next section lists states that still have conflicts.
+
+@example
+State 8 conflicts: 1 shift/reduce
+State 9 conflicts: 1 shift/reduce
+State 10 conflicts: 1 shift/reduce
+State 11 conflicts: 4 shift/reduce
@end example
@noindent
-The next section reproduces the exact grammar that Bison used:
+Then Bison reproduces the exact grammar it used:
@example
Grammar
- Number, Line, Rule
- 0 5 $accept -> exp $end
- 1 5 exp -> exp '+' exp
- 2 6 exp -> exp '-' exp
- 3 7 exp -> exp '*' exp
- 4 8 exp -> exp '/' exp
- 5 9 exp -> NUM
+ 0 $accept: exp $end
+
+ 1 exp: exp '+' exp
+ 2 | exp '-' exp
+ 3 | exp '*' exp
+ 4 | exp '/' exp
+ 5 | NUM
@end example
@noindent
'/' (47) 4
error (256)
NUM (258) 5
+STR (259)
@end group
@group
Nonterminals, with rules where they appear
-$accept (8)
+$accept (9)
on left: 0
-exp (9)
+exp (10)
on left: 1 2 3 4 5, on right: 0 1 2 3 4
@end group
@end example
@example
state 0
- $accept -> . exp $ (rule 0)
+ 0 $accept: . exp $end
- NUM shift, and go to state 1
+ NUM shift, and go to state 1
- exp go to state 2
+ exp go to state 2
@end example
This reads as follows: ``state 0 corresponds to being at the very
@example
state 0
- $accept -> . exp $ (rule 0)
- exp -> . exp '+' exp (rule 1)
- exp -> . exp '-' exp (rule 2)
- exp -> . exp '*' exp (rule 3)
- exp -> . exp '/' exp (rule 4)
- exp -> . NUM (rule 5)
+ 0 $accept: . exp $end
+ 1 exp: . exp '+' exp
+ 2 | . exp '-' exp
+ 3 | . exp '*' exp
+ 4 | . exp '/' exp
+ 5 | . NUM
- NUM shift, and go to state 1
+ NUM shift, and go to state 1
- exp go to state 2
+ exp go to state 2
@end example
@noindent
-In the state 1...
+In the state 1@dots{}
@example
state 1
- exp -> NUM . (rule 5)
+ 5 exp: NUM .
- $default reduce using rule 5 (exp)
+ $default reduce using rule 5 (exp)
@end example
@noindent
@example
state 2
- $accept -> exp . $ (rule 0)
- exp -> exp . '+' exp (rule 1)
- exp -> exp . '-' exp (rule 2)
- exp -> exp . '*' exp (rule 3)
- exp -> exp . '/' exp (rule 4)
+ 0 $accept: exp . $end
+ 1 exp: exp . '+' exp
+ 2 | exp . '-' exp
+ 3 | exp . '*' exp
+ 4 | exp . '/' exp
- $ shift, and go to state 3
- '+' shift, and go to state 4
- '-' shift, and go to state 5
- '*' shift, and go to state 6
- '/' shift, and go to state 7
+ $end shift, and go to state 3
+ '+' shift, and go to state 4
+ '-' shift, and go to state 5
+ '*' shift, and go to state 6
+ '/' shift, and go to state 7
@end example
@noindent
In state 2, the automaton can only shift a symbol. For instance,
-because of the item @samp{exp -> exp . '+' exp}, if the lookahead is
+because of the item @samp{exp: exp . '+' exp}, if the lookahead is
@samp{+} it is shifted onto the parse stack, and the automaton
-jumps to state 4, corresponding to the item @samp{exp -> exp '+' . exp}.
+jumps to state 4, corresponding to the item @samp{exp: exp '+' . exp}.
Since there is no default action, any lookahead not listed triggers a syntax
error.
@example
state 3
- $accept -> exp $ . (rule 0)
+ 0 $accept: exp $end .
- $default accept
+ $default accept
@end example
@noindent
-the initial rule is completed (the start symbol and the end
-of input were read), the parsing exits successfully.
+the initial rule is completed (the start symbol and the end-of-input were
+read), the parsing exits successfully.
The interpretation of states 4 to 7 is straightforward, and is left to
the reader.
@example
state 4
- exp -> exp '+' . exp (rule 1)
+ 1 exp: exp '+' . exp
+
+ NUM shift, and go to state 1
- NUM shift, and go to state 1
+ exp go to state 8
- exp go to state 8
state 5
- exp -> exp '-' . exp (rule 2)
+ 2 exp: exp '-' . exp
- NUM shift, and go to state 1
+ NUM shift, and go to state 1
+
+ exp go to state 9
- exp go to state 9
state 6
- exp -> exp '*' . exp (rule 3)
+ 3 exp: exp '*' . exp
+
+ NUM shift, and go to state 1
- NUM shift, and go to state 1
+ exp go to state 10
- exp go to state 10
state 7
- exp -> exp '/' . exp (rule 4)
+ 4 exp: exp '/' . exp
- NUM shift, and go to state 1
+ NUM shift, and go to state 1
- exp go to state 11
+ exp go to state 11
@end example
As was announced in beginning of the report, @samp{State 8 conflicts:
@example
state 8
- exp -> exp . '+' exp (rule 1)
- exp -> exp '+' exp . (rule 1)
- exp -> exp . '-' exp (rule 2)
- exp -> exp . '*' exp (rule 3)
- exp -> exp . '/' exp (rule 4)
+ 1 exp: exp . '+' exp
+ 1 | exp '+' exp .
+ 2 | exp . '-' exp
+ 3 | exp . '*' exp
+ 4 | exp . '/' exp
- '*' shift, and go to state 6
- '/' shift, and go to state 7
+ '*' shift, and go to state 6
+ '/' shift, and go to state 7
- '/' [reduce using rule 1 (exp)]
- $default reduce using rule 1 (exp)
+ '/' [reduce using rule 1 (exp)]
+ $default reduce using rule 1 (exp)
@end example
Indeed, there are two actions associated to the lookahead @samp{/}:
Because in deterministic parsing a single decision can be made, Bison
arbitrarily chose to disable the reduction, see @ref{Shift/Reduce, ,
-Shift/Reduce Conflicts}. Discarded actions are reported in between
+Shift/Reduce Conflicts}. Discarded actions are reported between
square brackets.
Note that all the previous states had a single possible action: either
@example
state 8
- exp -> exp . '+' exp (rule 1)
- exp -> exp '+' exp . [$, '+', '-', '/'] (rule 1)
- exp -> exp . '-' exp (rule 2)
- exp -> exp . '*' exp (rule 3)
- exp -> exp . '/' exp (rule 4)
+ 1 exp: exp . '+' exp
+ 1 | exp '+' exp . [$end, '+', '-', '/']
+ 2 | exp . '-' exp
+ 3 | exp . '*' exp
+ 4 | exp . '/' exp
- '*' shift, and go to state 6
- '/' shift, and go to state 7
+ '*' shift, and go to state 6
+ '/' shift, and go to state 7
- '/' [reduce using rule 1 (exp)]
- $default reduce using rule 1 (exp)
+ '/' [reduce using rule 1 (exp)]
+ $default reduce using rule 1 (exp)
+@end example
+
+Note however that while @samp{NUM + NUM / NUM} is ambiguous (which results in
+the conflicts on @samp{/}), @samp{NUM + NUM * NUM} is not: the conflict was
+solved thanks to associativity and precedence directives. If invoked with
+@option{--report=solved}, Bison includes information about the solved
+conflicts in the report:
+
+@example
+Conflict between rule 1 and token '+' resolved as reduce (%left '+').
+Conflict between rule 1 and token '-' resolved as reduce (%left '-').
+Conflict between rule 1 and token '*' resolved as shift ('+' < '*').
@end example
+
The remaining states are similar:
@example
@group
state 9
- exp -> exp . '+' exp (rule 1)
- exp -> exp . '-' exp (rule 2)
- exp -> exp '-' exp . (rule 2)
- exp -> exp . '*' exp (rule 3)
- exp -> exp . '/' exp (rule 4)
+ 1 exp: exp . '+' exp
+ 2 | exp . '-' exp
+ 2 | exp '-' exp .
+ 3 | exp . '*' exp
+ 4 | exp . '/' exp
- '*' shift, and go to state 6
- '/' shift, and go to state 7
+ '*' shift, and go to state 6
+ '/' shift, and go to state 7
- '/' [reduce using rule 2 (exp)]
- $default reduce using rule 2 (exp)
+ '/' [reduce using rule 2 (exp)]
+ $default reduce using rule 2 (exp)
@end group
@group
state 10
- exp -> exp . '+' exp (rule 1)
- exp -> exp . '-' exp (rule 2)
- exp -> exp . '*' exp (rule 3)
- exp -> exp '*' exp . (rule 3)
- exp -> exp . '/' exp (rule 4)
+ 1 exp: exp . '+' exp
+ 2 | exp . '-' exp
+ 3 | exp . '*' exp
+ 3 | exp '*' exp .
+ 4 | exp . '/' exp
- '/' shift, and go to state 7
+ '/' shift, and go to state 7
- '/' [reduce using rule 3 (exp)]
- $default reduce using rule 3 (exp)
+ '/' [reduce using rule 3 (exp)]
+ $default reduce using rule 3 (exp)
@end group
@group
state 11
- exp -> exp . '+' exp (rule 1)
- exp -> exp . '-' exp (rule 2)
- exp -> exp . '*' exp (rule 3)
- exp -> exp . '/' exp (rule 4)
- exp -> exp '/' exp . (rule 4)
+ 1 exp: exp . '+' exp
+ 2 | exp . '-' exp
+ 3 | exp . '*' exp
+ 4 | exp . '/' exp
+ 4 | exp '/' exp .
- '+' shift, and go to state 4
- '-' shift, and go to state 5
- '*' shift, and go to state 6
- '/' shift, and go to state 7
+ '+' shift, and go to state 4
+ '-' shift, and go to state 5
+ '*' shift, and go to state 6
+ '/' shift, and go to state 7
- '+' [reduce using rule 4 (exp)]
- '-' [reduce using rule 4 (exp)]
- '*' [reduce using rule 4 (exp)]
- '/' [reduce using rule 4 (exp)]
- $default reduce using rule 4 (exp)
+ '+' [reduce using rule 4 (exp)]
+ '-' [reduce using rule 4 (exp)]
+ '*' [reduce using rule 4 (exp)]
+ '/' [reduce using rule 4 (exp)]
+ $default reduce using rule 4 (exp)
@end group
@end example
range composed of a pair of @code{position}s (possibly spanning several
files).
-@deftypemethod {position} {std::string*} file
+@tindex uint
+In this section @code{uint} is an abbreviation for @code{unsigned int}: in
+genuine code only the latter is used.
+
+@menu
+* C++ position:: One point in the source file
+* C++ location:: Two points in the source file
+@end menu
+
+@node C++ position
+@subsubsection C++ @code{position}
+
+@deftypeop {Constructor} {position} {} position (std::string* @var{file} = 0, uint @var{line} = 1, uint @var{col} = 1)
+Create a @code{position} denoting a given point. Note that @code{file} is
+not reclaimed when the @code{position} is destroyed: memory managed must be
+handled elsewhere.
+@end deftypeop
+
+@deftypemethod {position} {void} initialize (std::string* @var{file} = 0, uint @var{line} = 1, uint @var{col} = 1)
+Reset the position to the given values.
+@end deftypemethod
+
+@deftypeivar {position} {std::string*} file
The name of the file. It will always be handled as a pointer, the
parser will never duplicate nor deallocate it. As an experimental
feature you may change it to @samp{@var{type}*} using @samp{%define
filename_type "@var{type}"}.
-@end deftypemethod
+@end deftypeivar
-@deftypemethod {position} {unsigned int} line
+@deftypeivar {position} {uint} line
The line, starting at 1.
-@end deftypemethod
+@end deftypeivar
-@deftypemethod {position} {unsigned int} lines (int @var{height} = 1)
+@deftypemethod {position} {uint} lines (int @var{height} = 1)
Advance by @var{height} lines, resetting the column number.
@end deftypemethod
-@deftypemethod {position} {unsigned int} column
-The column, starting at 0.
-@end deftypemethod
+@deftypeivar {position} {uint} column
+The column, starting at 1.
+@end deftypeivar
-@deftypemethod {position} {unsigned int} columns (int @var{width} = 1)
+@deftypemethod {position} {uint} columns (int @var{width} = 1)
Advance by @var{width} columns, without changing the line number.
@end deftypemethod
-@deftypemethod {position} {position&} operator+= (position& @var{pos}, int @var{width})
-@deftypemethodx {position} {position} operator+ (const position& @var{pos}, int @var{width})
-@deftypemethodx {position} {position&} operator-= (const position& @var{pos}, int @var{width})
-@deftypemethodx {position} {position} operator- (position& @var{pos}, int @var{width})
+@deftypemethod {position} {position&} operator+= (int @var{width})
+@deftypemethodx {position} {position} operator+ (int @var{width})
+@deftypemethodx {position} {position&} operator-= (int @var{width})
+@deftypemethodx {position} {position} operator- (int @var{width})
Various forms of syntactic sugar for @code{columns}.
@end deftypemethod
-@deftypemethod {position} {position} operator<< (std::ostream @var{o}, const position& @var{p})
+@deftypemethod {position} {bool} operator== (const position& @var{that})
+@deftypemethodx {position} {bool} operator!= (const position& @var{that})
+Whether @code{*this} and @code{that} denote equal/different positions.
+@end deftypemethod
+
+@deftypefun {std::ostream&} operator<< (std::ostream& @var{o}, const position& @var{p})
Report @var{p} on @var{o} like this:
@samp{@var{file}:@var{line}.@var{column}}, or
@samp{@var{line}.@var{column}} if @var{file} is null.
+@end deftypefun
+
+@node C++ location
+@subsubsection C++ @code{location}
+
+@deftypeop {Constructor} {location} {} location (const position& @var{begin}, const position& @var{end})
+Create a @code{Location} from the endpoints of the range.
+@end deftypeop
+
+@deftypeop {Constructor} {location} {} location (const position& @var{pos} = position())
+@deftypeopx {Constructor} {location} {} location (std::string* @var{file}, uint @var{line}, uint @var{col})
+Create a @code{Location} denoting an empty range located at a given point.
+@end deftypeop
+
+@deftypemethod {location} {void} initialize (std::string* @var{file} = 0, uint @var{line} = 1, uint @var{col} = 1)
+Reset the location to an empty range at the given values.
@end deftypemethod
-@deftypemethod {location} {position} begin
-@deftypemethodx {location} {position} end
+@deftypeivar {location} {position} begin
+@deftypeivarx {location} {position} end
The first, inclusive, position of the range, and the first beyond.
-@end deftypemethod
+@end deftypeivar
-@deftypemethod {location} {unsigned int} columns (int @var{width} = 1)
-@deftypemethodx {location} {unsigned int} lines (int @var{height} = 1)
+@deftypemethod {location} {uint} columns (int @var{width} = 1)
+@deftypemethodx {location} {uint} lines (int @var{height} = 1)
Advance the @code{end} position.
@end deftypemethod
-@deftypemethod {location} {location} operator+ (const location& @var{begin}, const location& @var{end})
-@deftypemethodx {location} {location} operator+ (const location& @var{begin}, int @var{width})
-@deftypemethodx {location} {location} operator+= (const location& @var{loc}, int @var{width})
+@deftypemethod {location} {location} operator+ (const location& @var{end})
+@deftypemethodx {location} {location} operator+ (int @var{width})
+@deftypemethodx {location} {location} operator+= (int @var{width})
Various forms of syntactic sugar.
@end deftypemethod
Move @code{begin} onto @code{end}.
@end deftypemethod
+@deftypemethod {location} {bool} operator== (const location& @var{that})
+@deftypemethodx {location} {bool} operator!= (const location& @var{that})
+Whether @code{*this} and @code{that} denote equal/different ranges of
+positions.
+@end deftypemethod
+
+@deftypefun {std::ostream&} operator<< (std::ostream& @var{o}, const location& @var{p})
+Report @var{p} on @var{o}, taking care of special cases such as: no
+@code{filename} defined, or equal filename/line or column.
+@end deftypefun
@node C++ Parser Interface
@subsection C++ Parser Interface
Use @code{%code init} for code added to the start of the constructor
body. This is especially useful to initialize superclasses. Use
-@samp{%define init_throws} to specify any uncatch exceptions.
+@samp{%define init_throws} to specify any uncaught exceptions.
@end deftypeop
@deftypemethod {YYParser} {boolean} parse ()
@c LocalWords: NUM exp subsubsection kbd Ctrl ctype EOF getchar isdigit nonfree
@c LocalWords: ungetc stdin scanf sc calc ulator ls lm cc NEG prec yyerrok rr
@c LocalWords: longjmp fprintf stderr yylloc YYLTYPE cos ln Stallman Destructor
-@c LocalWords: symrec val tptr FNCT fnctptr func struct sym enum
+@c LocalWords: symrec val tptr FNCT fnctptr func struct sym enum IEC syntaxes
@c LocalWords: fnct putsym getsym fname arith fncts atan ptr malloc sizeof Lex
@c LocalWords: strlen strcpy fctn strcmp isalpha symbuf realloc isalnum DOTDOT
@c LocalWords: ptypes itype YYPRINT trigraphs yytname expseq vindex dtype Unary
@c LocalWords: strncmp intval tindex lvalp locp llocp typealt YYBACKUP subrange
@c LocalWords: YYEMPTY YYEOF YYRECOVERING yyclearin GE def UMINUS maybeword loc
@c LocalWords: Johnstone Shamsa Sadaf Hussain Tomita TR uref YYMAXDEPTH inline
-@c LocalWords: YYINITDEPTH stmts ref initdcl maybeasm notype Lookahead
+@c LocalWords: YYINITDEPTH stmts ref initdcl maybeasm notype Lookahead yyoutput
@c LocalWords: hexflag STR exdent itemset asis DYYDEBUG YYFPRINTF args Autoconf
@c LocalWords: infile ypp yxx outfile itemx tex leaderfill Troubleshouting sqrt
@c LocalWords: hbox hss hfill tt ly yyin fopen fclose ofirst gcc ll lookahead
@c LocalWords: nbar yytext fst snd osplit ntwo strdup AST Troublereporting th
@c LocalWords: YYSTACK DVI fdl printindex IELR nondeterministic nonterminals ps
@c LocalWords: subexpressions declarator nondeferred config libintl postfix LAC
-@c LocalWords: preprocessor nonpositive unary nonnumeric typedef extern rhs
-@c LocalWords: yytokentype destructor multicharacter nonnull EBCDIC
+@c LocalWords: preprocessor nonpositive unary nonnumeric typedef extern rhs sr
+@c LocalWords: yytokentype destructor multicharacter nonnull EBCDIC nterm LR's
@c LocalWords: lvalue nonnegative XNUM CHR chr TAGLESS tagless stdout api TOK
-@c LocalWords: destructors Reentrancy nonreentrant subgrammar nonassociative
+@c LocalWords: destructors Reentrancy nonreentrant subgrammar nonassociative Ph
@c LocalWords: deffnx namespace xml goto lalr ielr runtime lex yacc yyps env
@c LocalWords: yystate variadic Unshift NLS gettext po UTF Automake LOCALEDIR
@c LocalWords: YYENABLE bindtextdomain Makefile DEFS CPPFLAGS DBISON DeRemer
-@c LocalWords: autoreconf Pennello multisets nondeterminism Generalised baz
+@c LocalWords: autoreconf Pennello multisets nondeterminism Generalised baz ACM
@c LocalWords: redeclare automata Dparse localedir datadir XSLT midrule Wno
-@c LocalWords: Graphviz multitable headitem hh basename Doxygen fno
+@c LocalWords: Graphviz multitable headitem hh basename Doxygen fno filename
@c LocalWords: doxygen ival sval deftypemethod deallocate pos deftypemethodx
@c LocalWords: Ctor defcv defcvx arg accessors arithmetics CPP ifndef CALCXX
@c LocalWords: lexer's calcxx bool LPAREN RPAREN deallocation cerrno climits
@c LocalWords: cstdlib Debian undef yywrap unput noyywrap nounput zA yyleng
-@c LocalWords: errno strtol ERANGE str strerror iostream argc argv Javadoc
+@c LocalWords: errno strtol ERANGE str strerror iostream argc argv Javadoc PSLR
@c LocalWords: bytecode initializers superclass stype ASTNode autoboxing nls
@c LocalWords: toString deftypeivar deftypeivarx deftypeop YYParser strictfp
@c LocalWords: superclasses boolean getErrorVerbose setErrorVerbose deftypecv
@c LocalWords: getDebugStream setDebugStream getDebugLevel setDebugLevel url
@c LocalWords: bisonVersion deftypecvx bisonSkeleton getStartPos getEndPos
-@c LocalWords: getLVal defvar deftypefn deftypefnx gotos msgfmt Corbett
-@c LocalWords: subdirectory Solaris nonassociativity
+@c LocalWords: getLVal defvar deftypefn deftypefnx gotos msgfmt Corbett LALR's
+@c LocalWords: subdirectory Solaris nonassociativity perror schemas Malloy
+@c LocalWords: Scannerless ispell american
@c Local Variables:
@c ispell-dictionary: "american"
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