gram.y

編譯器的虛擬yacc工具

%{
#include <stdio.h>
#define T 3
extern yylineno;
%}

%token PROGRAM_T INTEGER_T REAL_T OF_T VAR_T ARRAY_T
%token PROCEDURE_T FUNCTION_T BEGIN_T END_T ELSE_T THEN_T DO_T
%token READ_T WRITE_T IF_T WHILE_T
%token ASSIGN_OP DOTDOT NOT_T
%token ID NUM REAL_NUM

%left REL_OP
%left AND_T OR_T
%left NOT_T
%left '+' '-'
%left '*' '/' MOD_T

%%

program         :       PROGRAM_T ID '('  id_list ')' ';'
                        declarations
                        subprograms
                        compound_stmt '.'
                ;

id_list         :       id_list ',' ID
                |       ID
                ;

declarations    :       declarations VAR_T id_list ':' type ';'
                |       
                ;

type            :       standard_type
                |       ARRAY_T '[' NUM DOTDOT NUM ']' OF_T standard_type
                ;

standard_type   :       INTEGER_T
                |       REAL_T
                ;

subprograms     :       subprograms subprogram ';'
                |       {/* empty */}
                ;

subprogram      :       subprogram_head declarations compound_stmt
                ;

subprogram_head :       FUNCTION_T ID arguments ':' standard_type ';'
                |       PROCEDURE_T ID arguments ';'
                ;

arguments       :       '(' param_list ')'
                |       {/* empty */}
                ;

param_list      :       param_list ';' id_list ':' type
                |       id_list ':' type
                ;

compound_stmt   :       BEGIN_T opt_stmts END_T
                ;

opt_stmts       :       stmt_list
                |       {/* empty */}
                ;

stmt_list       :       stmt
                |       stmt_list ';' stmt
                ;


stmt            :       ID ASSIGN_OP expression
                |       ID '[' expression ']' ASSIGN_OP expression
                |       procedure_stmt
                |       compound_stmt
                |       IF_T expression THEN_T stmt ELSE_T stmt
                |       WHILE_T expression DO_T stmt
                |       READ_T '(' variable_list ')'
                |       WRITE_T '(' expression_list ')'
                ;

variable_list   :       variable_list ',' variable
                |       variable
                ;

variable        :       ID
                |       ID '[' expression ']'
                ;

procedure_stmt  :       ID
                |       ID '(' expression_list ')'
                ;

expression_list :       expression_list ',' expression
                |       expression
                ;

expression      :       expression REL_OP expression
                |       expression '+' expression
                |       expression '-' expression
                |       expression '*' expression
                |       expression '/' expression
                |       expression MOD_T expression
                |       expression AND_T expression
                |       expression OR_T expression
                |       NOT_T expression
                |       '-' expression
                |       ID      
                |       ID '[' expression ']'
                |       ID '(' expression_list ')'
                |       NUM
                |       REAL_NUM
                |       '(' expression ')'
                ;


%%

yyerror()
{
  printf("Syntax error line %d\n",yylineno);
}