1 /**

     2  * test/demos/parser/parser.yy

     3  * Copyright (C) 2008 Markus Broeker

     4  */

     5 

     6 %{

     7    #include <stdio.h>

     8    #include <ctype.h>

     9 

    10    int regs[26]; 

    11    int base;

    12 	

    13    int yyerror();

    14    int yylex();

    15 %}

    16 

    17 %start list

    18 %token DIGIT LETTER

    19 %left MINUS PLUS MUL DIV

    20 %left UMINUS

    21 %%

    22 

    23 list : /* empty */ 

    24 	| list stat '\n' 

    25 	| list error '\n' { yyerrok; };

    26 

    27 stat : 

    28 	expr { (void) printf( "RESULT: %d\n", $1 ); } 

    29 	| LETTER '=' expr { regs[$1] = $3; }

    30 	;

    31 

    32    expr      :  '(' expr ')'

    33              {

    34                    $$ = $2;

    35              }

    36              |  expr PLUS expr

    37              {

    38                    $$ = $1 + $3;

    39              }

    40              |  expr MINUS expr

    41              {

    42                    $$ = $1 - $3;

    43              }

    44              |  expr MUL expr

    45              { 

    46                    $$ = $1 * $3;

    47              }

    48              |  expr DIV expr

    49              {

    50                    $$ = $1 / $3;

    51              }

    52              |  MINUS expr  %prec UMINUS

    53              {

    54                    $$ = -$2;

    55              }

    56              |  LETTER

    57              {

    58                    $$ = regs[$1];

    59              }

    60              |  number

    61              ;

    62 

    63    number    :   DIGIT

    64              {

    65                     $$ = $1; base = ($1==0) ? 8 : 10;

    66              }

    67              |   number DIGIT

    68              {

    69                     $$ = base * $1 + $2;

    70              }

    71              ;

    72    

    73 %%

    74 

    75 int yyerror() 

    76 {

    77 	printf("ERROR\n");

    78 	return 0;

    79 }

    80 

    81 int yywrap() 

    82 {

    83 	return 1;

    84 }