pas.y

Yacc例子代码

/* PAS.Y: ISO Level 0 Pascal grammar, adapted to TP Yacc 2-28-89 AG
   To compile: yacc pas
               lex paslex
               tpc pas */

%{
(*
 *
 * Pascal grammar in Yacc format, based originally on BNF given
 * in "Standard Pascal -- User Reference Manual", by Doug Cooper.
 * This in turn is the BNF given by the ANSI and ISO Pascal standards,
 * and so, is PUBLIC DOMAIN. The grammar is for ISO Level 0 Pascal.
 * The grammar has been massaged somewhat to make it LALR, and added
 * the following extensions.
 *
 * constant expressions
 * otherwise statement in a case
 * productions to correctly match else's with if's
 * beginnings of a separate compilation facility
 *
 *)

uses LexLib, YaccLib;

var filename : String;

procedure yyerror(msg : string);
  begin
    writeln(filename, ': ', yylineno, ': ',
            msg, ' at or before `', yytext, '''.')
  end(*yyerror*);

%}

/* Note the Pascal keyword tokens are stropped with leading underscore
   (e.g. _AND) in the Turbo Pascal Yacc version, because these identifiers
   will be declared as token numbers in the output file generated by Yacc,
   and hence must not collide with Turbo Pascal keywords. */

%token _AND _ARRAY ASSIGNMENT _BEGIN _CASE CHARACTER_STRING COLON COMMA _CONST DIGSEQ
%token _DIV _DO DOT DOTDOT _DOWNTO _ELSE _END EQUAL _EXTERNAL _FILE _FOR _FORWARD _FUNCTION
%token GE _GOTO GT IDENTIFIER _IF _IN _LABEL LBRAC LE LPAREN LT MINUS _MOD _NIL _NOT
%token NOTEQUAL _OF _OR _OTHERWISE _PACKED PLUS _PROCEDURE _PROGRAM RBRAC
%token REALNUMBER _RECORD _REPEAT RPAREN SEMICOLON _SET SLASH STAR STARSTAR _THEN
%token _TO _TYPE _UNTIL UPARROW _VAR _WHILE _WITH

%token ILLEGAL

%%

file : program
    | program error
	{ writeln(yylineno, ':Text follows logical end of program.'); }
    | module
    ;

program : program_heading semicolon block DOT
    ;

program_heading : _PROGRAM identifier
    | _PROGRAM identifier LPAREN identifier_list RPAREN
    ;

identifier_list : identifier_list comma identifier
    | identifier
    ;

block : label_declaration_part
    constant_definition_part
    type_definition_part
    variable_declaration_part
    procedure_and_function_declaration_part
    statement_part
    ;

module : constant_definition_part
    type_definition_part
    variable_declaration_part
    procedure_and_function_declaration_part
    ;

label_declaration_part : _LABEL label_list semicolon
    |
    ;

label_list : label_list comma label
    | label
    ;

label : DIGSEQ
    ;

constant_definition_part : _CONST constant_list
    |
    ;

constant_list : constant_list constant_definition
    | constant_definition
    ;

constant_definition : identifier EQUAL cexpression semicolon
    ;

/*constant : cexpression ;        /* good stuff! */

cexpression : csimple_expression
    | csimple_expression relop csimple_expression
    ;

csimple_expression : cterm
    | csimple_expression addop cterm
    ;

cterm : cfactor
    | cterm mulop cfactor
    ;

cfactor : sign cfactor
    | cexponentiation
    ;

cexponentiation : cprimary
    | cprimary STARSTAR cexponentiation
    ;

cprimary : identifier
    | LPAREN cexpression RPAREN
    | unsigned_constant
    | _NOT cprimary
    ;

constant : non_string
    | sign non_string
    | CHARACTER_STRING
    ;

sign : PLUS
    | MINUS
    ;

non_string : DIGSEQ
    | identifier
    | REALNUMBER
    ;

type_definition_part : _TYPE type_definition_list
    |
    ;

type_definition_list : type_definition_list type_definition
    | type_definition
    ;

type_definition : identifier EQUAL type_denoter semicolon
    ;

type_denoter : identifier
    | new_type
    ;

new_type : new_ordinal_type
    | new_structured_type
    | new_pointer_type
    ;

new_ordinal_type : enumerated_type
    | subrange_type
    ;

enumerated_type : LPAREN identifier_list RPAREN
    ;

subrange_type : constant DOTDOT constant
    ;

new_structured_type : structured_type
    | _PACKED structured_type
    ;

structured_type : array_type
    | record_type
    | set_type
    | file_type
    ;

array_type : _ARRAY LBRAC index_list RBRAC _OF component_type
    ;

index_list : index_list comma index_type
    | index_type
    ;

index_type : ordinal_type ;

ordinal_type : new_ordinal_type
    | identifier
    ;

component_type : type_denoter ;

record_type : _RECORD record_section_list _END
    | _RECORD record_section_list semicolon variant_part _END
    | _RECORD variant_part _END
    ;

record_section_list : record_section_list semicolon record_section
    | record_section
    ;

record_section : identifier_list COLON type_denoter
    ;

variant_part : _CASE variant_selector _OF variant_list semicolon
    | _CASE variant_selector _OF variant_list
    |
    ;

variant_selector : tag_field COLON tag_type
    | tag_type
    ;

variant_list : variant_list semicolon variant
    | variant
    ;

variant : case_constant_list COLON LPAREN record_section_list RPAREN
    | case_constant_list COLON LPAREN record_section_list semicolon
        variant_part RPAREN
    | case_constant_list COLON LPAREN variant_part RPAREN
    ;

case_constant_list : case_constant_list comma case_constant
    | case_constant
    ;

case_constant : constant
    | constant DOTDOT constant
    ;

tag_field : identifier ;

tag_type : identifier ;

set_type : _SET _OF base_type
    ;

base_type : ordinal_type ;

file_type : _FILE _OF component_type
    ;

new_pointer_type : UPARROW domain_type
    ;

domain_type : identifier ;

variable_declaration_part : _VAR variable_declaration_list semicolon
    |
    ;

variable_declaration_list :
      variable_declaration_list semicolon variable_declaration
    | variable_declaration
    ;

variable_declaration : identifier_list COLON type_denoter
    ;

procedure_and_function_declaration_part :
        proc_or_func_declaration_list semicolon
    |
    ;

proc_or_func_declaration_list :
      proc_or_func_declaration_list semicolon proc_or_func_declaration
    | proc_or_func_declaration
    ;

proc_or_func_declaration : procedure_declaration
    | function_declaration
    ;

procedure_declaration : procedure_heading semicolon directive
    | procedure_heading semicolon procedure_block
    ;

procedure_heading : procedure_identification
    | procedure_identification formal_parameter_list
    ;

directive : _FORWARD
    | _EXTERNAL
    ;

formal_parameter_list : LPAREN formal_parameter_section_list RPAREN ;

formal_parameter_section_list : formal_parameter_section_list semicolon
 formal_parameter_section
    | formal_parameter_section
    ;

formal_parameter_section : value_parameter_specification
    | variable_parameter_specification
    | procedural_parameter_specification
    | functional_parameter_specification
    ;

value_parameter_specification : identifier_list COLON identifier
    ;

variable_parameter_specification : _VAR identifier_list COLON identifier
    ;

procedural_parameter_specification : procedure_heading ;

functional_parameter_specification : function_heading ;

procedure_identification : _PROCEDURE identifier ;

procedure_block : block ;

function_declaration : function_heading semicolon directive
    | function_identification semicolon function_block
    | function_heading semicolon function_block
    ;

function_heading : _FUNCTION identifier COLON result_type
    | _FUNCTION identifier formal_parameter_list COLON result_type
    ;

result_type : identifier ;

function_identification : _FUNCTION identifier ;

function_block : block ;

statement_part : compound_statement ;

compound_statement : _BEGIN statement_sequence _END ;

statement_sequence : statement_sequence semicolon statement
    | statement
    | error
 { writeln('statement ignored'); yyclearin }
    ;

statement : open_statement
    | closed_statement
    ;

open_statement : label COLON non_labeled_open_statement
    | non_labeled_open_statement
    ;

closed_statement : label COLON non_labeled_closed_statement
    | non_labeled_closed_statement
    ;

non_labeled_closed_statement : assignment_statement
    | procedure_statement
    | goto_statement
    | compound_statement
    | case_statement
    | repeat_statement
    | closed_with_statement
    | closed_if_statement
    | closed_while_statement
    | closed_for_statement
    |
    ;

non_labeled_open_statement : open_with_statement
    | open_if_statement
    | open_while_statement
    | open_for_statement
    ;

repeat_statement : _REPEAT statement_sequence _UNTIL boolean_expression
    ;

open_while_statement : _WHILE boolean_expression _DO open_statement
    ;

closed_while_statement : _WHILE boolean_expression _DO closed_statement
    ;

open_for_statement : _FOR control_variable ASSIGNMENT initial_value direction
            final_value _DO open_statement
    ;

closed_for_statement : _FOR control_variable ASSIGNMENT initial_value direction
            final_value _DO closed_statement
    ;

open_with_statement : _WITH record_variable_list _DO open_statement
    ;

closed_with_statement : _WITH record_variable_list _DO closed_statement
    ;

open_if_statement : _IF boolean_expression _THEN statement
    | _IF boolean_expression _THEN closed_statement _ELSE open_statement
    ;

closed_if_statement : _IF boolean_expression _THEN closed_statement
            _ELSE closed_statement
    ;

assignment_statement : variable_access ASSIGNMENT expression
    ;

variable_access : identifier
    | indexed_variable
    | field_designator
    | variable_access UPARROW
    ;

indexed_variable : variable_access LBRAC index_expression_list RBRAC
    ;

index_expression_list : index_expression_list comma index_expression
    | index_expression
    ;

index_expression : expression ;

field_designator : variable_access DOT identifier
    ;

procedure_statement : identifier params
    | identifier
    ;

params : LPAREN actual_parameter_list RPAREN ;

actual_parameter_list : actual_parameter_list comma actual_parameter
    | actual_parameter
    ;

/*
 * this forces you to check all this to be sure that only write and
 * writeln use the 2nd and 3rd forms, you really can't do it easily in
 * the grammar, especially since write and writeln aren't reserved
 */
actual_parameter : expression
    | expression COLON expression
    | expression COLON expression COLON expression
    ;

goto_statement : _GOTO label
    ;

case_statement : _CASE case_index _OF case_list_element_list _END
    | _CASE case_index _OF case_list_element_list SEMICOLON _END
    | _CASE case_index _OF case_list_element_list semicolon
            otherwisepart statement _END
    | _CASE case_index _OF case_list_element_list semicolon
            otherwisepart statement SEMICOLON _END
    ;

case_index : expression ;

case_list_element_list : case_list_element_list semicolon case_list_element
    | case_list_element
    ;

case_list_element : case_constant_list COLON statement
    ;

otherwisepart :    _OTHERWISE
    | _OTHERWISE COLON
    ;

control_variable : identifier ;

initial_value : expression ;

direction : _TO
    | _DOWNTO
    ;

final_value : expression ;

record_variable_list : record_variable_list comma variable_access
    | variable_access
    ;

boolean_expression : expression ;

expression : simple_expression
    | simple_expression relop simple_expression
    | error
    ;

simple_expression : term
    | simple_expression addop term
    ;

term : factor
    | term mulop factor
    ;

factor : sign factor
    | exponentiation
    ;

exponentiation : primary
    | primary STARSTAR exponentiation
    ;

primary : variable_access
    | unsigned_constant
    | function_designator
    | set_constructor
    | LPAREN expression RPAREN
    | _NOT primary
    ;

unsigned_constant : unsigned_number
    | CHARACTER_STRING
    | _NIL
    ;

unsigned_number : unsigned_integer | unsigned_real ;

unsigned_integer : DIGSEQ
    ;

unsigned_real : REALNUMBER
    ;

/* functions with no params will be handled by plain identifier */
function_designator : identifier params
    ;

set_constructor : LBRAC member_designator_list RBRAC
    | LBRAC RBRAC
    ;

member_designator_list : member_designator_list comma member_designator
    | member_designator
    ;

member_designator : member_designator DOTDOT expression
    | expression
    ;

addop: PLUS
    | MINUS
    | _OR
    ;

mulop : STAR
    | SLASH
    | _DIV
    | _MOD
    | _AND
    ;

relop : EQUAL
    | NOTEQUAL
    | LT
    | GT
    | LE
    | GE
    | _IN
    ;

identifier : IDENTIFIER
    ;

semicolon : SEMICOLON
    ;

comma : COMMA
    ;

%%

{$I paslex.pas}

begin
  filename := paramStr(1);
  if filename='' then
    begin
      write('input file: ');
      readln(filename);
    end;
  assign(yyinput, filename);
  reset(yyinput);
  if yyparse=0 then writeln('successful parse!');
end.