Grammar Documentation

grammar_file

entry point

The top-level rule. A Bison grammar file consists of an optional
prologue, a declarations section, the first "%%" separator, one or
more grammar rules, and an optional epilogue.

Grammar definition

grammar_file
    : prologue_opt declarations "%%" rules epilogue_opt
    ;

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References

prologue_opt declarations rules epilogue_opt

prologue_opt

An optional C declarations block enclosed in "%{" and "%}".
Contents are copied verbatim to the top of the generated parser
file, before the definition of yyparse. May be omitted entirely
if no C declarations are needed.

Grammar definition

prologue_opt
    : /* empty */
    | "%{" PROLOGUE_CONTENT "%}"
    ;

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Referenced by

grammar_file

References

PROLOGUE_CONTENT

epilogue_opt

An optional epilogue section introduced by a second "%%".
Contains arbitrary C code copied verbatim to the end of the
generated parser file. May be omitted if empty.

Grammar definition

epilogue_opt
    : /* empty */
    | "%%" EPILOGUE_CONTENT
    ;

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Referenced by

grammar_file

References

EPILOGUE_CONTENT

declarations

Zero or more Bison declarations appearing before the first "%%".
Declarations define terminal and nonterminal symbols, specify
operator precedence and associativity, and configure parser
options.

Grammar definition

declarations
    : /* empty */
    | declarations declaration
    ;

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Referenced by

grammar_file

References

declarations declaration

declaration

A single Bison declaration. Covers token declarations, precedence
and associativity declarations, type annotations, union definitions,
start symbol, conflict suppression, and various parser directives.
A bare action block may also appear as a declaration.

Grammar definition

declaration
    : "%token"       tag_opt symbol_list
    | "%left"        tag_opt symbol_list
    | "%right"       tag_opt symbol_list
    | "%nonassoc"    tag_opt symbol_list
    | "%type"        tag     nonterminal_list
    | "%union"       ACTION_CONTENT
    | "%start"       IDENTIFIER
    | "%expect"      INTEGER
    | "%pure_parser"
    | "%error_verbose"
    | "%defines"
    | "%locations"
    | "%glr-parser"
    | "%skeleton"    STRING_LITERAL
    | "%output"      STRING_LITERAL
    | "%name-prefix" STRING_LITERAL
    | "%require"     STRING_LITERAL
    | "%prec"        symbol
    | ACTION_CONTENT
    ;

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Referenced by

declarations

References

tag_opt symbol_list tag nonterminal_listACTION_CONTENTIDENTIFIERINTEGERSTRING_LITERALsymbol

tag_opt

An optional type tag used in token, precedence, and type
declarations to associate a semantic value type from the %union
with a symbol. Enclosed in angle brackets. e.g. <val>

Grammar definition

tag_opt
    : /* empty */
    | tag
    ;

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Referenced by

declaration

References

tag

A type tag. An identifier enclosed in angle brackets referring to
a member name in the %union declaration.
e.g. "<val>", "<tptr>"

Grammar definition

tag
    : "<" IDENTIFIER ">"
    ;

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Referenced by

declaration tag_opt

References

IDENTIFIER

symbol_list

A non-empty list of symbol declarations appearing after a %token,
%left, %right, or %nonassoc directive.

Grammar definition

symbol_list
    : symbol_decl
    | symbol_list symbol_decl
    ;

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Referenced by

declaration

References

symbol_decl symbol_list

symbol_decl

A single symbol declaration within a token or precedence directive.
May be a named token identifier, a named token with an explicit
numeric code, or a character literal token.
e.g. NUM, NUM 300, '+'

Grammar definition

symbol_decl
    : IDENTIFIER
    | IDENTIFIER INTEGER
    | CHAR_LITERAL
    ;

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Referenced by

symbol_list

References

IDENTIFIERINTEGERCHAR_LITERAL

nonterminal_list

A non-empty list of nonterminal symbol names following a %type
directive. All listed nonterminals are assigned the type specified
by the preceding tag.

Grammar definition

nonterminal_list
    : IDENTIFIER
    | nonterminal_list IDENTIFIER
    ;

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Referenced by

declaration

References

IDENTIFIERnonterminal_list

rules

One or more grammar rules appearing after the first "%%".

Grammar definition

rules
    : rule
    | rules rule
    ;

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Referenced by

grammar_file

References

rule rules

rule

A single grammar rule. A nonterminal symbol name followed by ":",
one or more alternatives separated by "|", and terminated by ";".
e.g. expr : expr "+" term | term ;

Grammar definition

rule
    : IDENTIFIER ":" rule_alternatives ";"
    ;

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Referenced by

rules

References

IDENTIFIERrule_alternatives

rule_alternatives

A list of one or more rule alternatives separated by "|". Each
alternative defines one way to derive the rule's nonterminal.

Grammar definition

rule_alternatives
    : rule_rhs
    | rule_alternatives "|" rule_rhs
    ;

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Referenced by

rule

References

rule_rhs rule_alternatives

rule_rhs

A single rule alternative. A sequence of zero or more symbols,
mid-rule action blocks, and optional "%prec" precedence overrides.
An empty alternative matches the empty string (epsilon).

Grammar definition

rule_rhs
    : /* empty */
    | rule_rhs symbol
    | rule_rhs ACTION_CONTENT
    | rule_rhs "%prec" symbol
    ;

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Referenced by

rule_alternatives

References

rule_rhs symbolACTION_CONTENT

symbol

A grammar symbol appearing in a rule alternative. May be a named
token or nonterminal identifier, a character literal token, or a
string alias for a token.

Grammar definition

symbol
    : IDENTIFIER
    | CHAR_LITERAL
    | STRING_LITERAL
    ;

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Referenced by

declaration rule_rhs

References

IDENTIFIERCHAR_LITERALSTRING_LITERAL