exp/expression-parser.y

   1 %{
   2
   3 /*
   4  * (C) Copyright 2014, Stephen M. Cameron.
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License version 2 as
   8  *  published by the Free Software Foundation.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with this program; if not, write to the Free Software
  17  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18  *
  19  */
  20
  21 #include <stdio.h>
  22 #include <string.h>
  23
  24 struct parser_value_type {
  25         double dval;
  26         long long ival;
  27         int has_dval;
  28         int has_error;
  29 };
  30
  31 typedef union valtype {
  32         struct parser_value_type v;
  33 } PARSER_VALUE_TYPE;
  34
  35 #define YYSTYPE PARSER_VALUE_TYPE
  36
  37 int yyerror(__attribute__((unused)) long long *result,
  38                 __attribute__((unused)) double *dresult,
  39                 __attribute__((unused)) int *has_error,
  40                 __attribute__((unused)) int *bye, const char *msg);
  41
  42 extern int yylex(void);
  43 extern void yyrestart(FILE *file);
  44
  45 %}
  46
  47 %union valtype {
  48         struct parser_value_type {
  49                 double dval;
  50                 long long ival;
  51                 int has_dval;
  52                 int has_error;
  53         } v;
  54 };
  55
  56 %token <v> NUMBER
  57 %token <v> BYE
  58 %left '-' '+'
  59 %left '*' '/'
  60 %nonassoc UMINUS
  61 %parse-param { long long *result }
  62 %parse-param { double *dresult }
  63 %parse-param { int *has_error }
  64 %parse-param { int *bye }
  65
  66 %type <v> expression
  67 %%
  68
  69 top_level:      expression {
  70                                 *result = $1.ival;
  71                                 *dresult = $1.dval;
  72                                 *has_error = $1.has_error;
  73                         }
  74                 | expression error {
  75                                 *result = $1.ival;
  76                                 *dresult = $1.dval;
  77                                 *has_error = 1;
  78                         }
  79 expression:     expression '+' expression {
  80                         if (!$1.has_dval && !$3.has_dval)
  81                                 $$.ival = $1.ival + $3.ival;
  82                         else
  83                                 $$.ival = (long long) ($1.dval + $3.dval);
  84                         $$.dval = $1.dval + $3.dval;
  85                         $$.has_error = $1.has_error || $3.has_error;
  86                 }
  87         |       expression '-' expression {
  88                         if (!$1.has_dval && !$3.has_dval)
  89                                 $$.ival = $1.ival - $3.ival;
  90                         else
  91                                 $$.ival = (long long) ($1.dval - $3.dval);
  92                         $$.dval = $1.dval - $3.dval;
  93                         $$.has_error = $1.has_error || $3.has_error;
  94                 }
  95         |       expression '*' expression {
  96                         if (!$1.has_dval && !$3.has_dval)
  97                                 $$.ival = $1.ival * $3.ival;
  98                         else
  99                                 $$.ival = (long long) ($1.dval * $3.dval);
 100                         $$.dval = $1.dval * $3.dval;
 101                         $$.has_error = $1.has_error || $3.has_error;
 102                 }
 103         |       expression '/' expression {
 104                         if ($3.ival == 0)
 105                                 yyerror(0, 0, 0, 0, "divide by zero");
 106                         else
 107                                 $$.ival = $1.ival / $3.ival;
 108                         if ($3.dval < 1e-20 && $3.dval > -1e-20)
 109                                 yyerror(0, 0, 0, 0, "divide by zero");
 110                         else
 111                                 $$.dval = $1.dval / $3.dval;
 112                         if ($3.has_dval || $1.has_dval)
 113                                 $$.ival = (long long) $$.dval;
 114                         $$.has_error = $1.has_error || $3.has_error;
 115                 }
 116         |       '-' expression %prec UMINUS {
 117                         $$.ival = -$2.ival;
 118                         $$.dval = -$2.dval;
 119                         $$.has_error = $2.has_error;
 120                 }
 121         |       '(' expression ')' { $$ = $2; }
 122         |       NUMBER { $$ = $1; }
 123         |       BYE { $$ = $1; *bye = 1; };
 124 %%
 125 #include <stdio.h>
 126
 127 /* Urgh.  yacc and lex are kind of horrible.  This is not thread safe, obviously. */
 128 static int lexer_read_offset = 0;
 129 static char lexer_input_buffer[1000];
 130
 131 int lexer_input(char* buffer, int *bytes_read, int bytes_requested)
 132 {
 133         int bytes_left = strlen(lexer_input_buffer) - lexer_read_offset;
 134
 135         if (bytes_requested > bytes_left )
 136                 bytes_requested = bytes_left;
 137         memcpy(buffer, &lexer_input_buffer[lexer_read_offset], bytes_requested);
 138         *bytes_read = bytes_requested;
 139         lexer_read_offset += bytes_requested;
 140         return 0;
 141 }
 142
 143 static void setup_to_parse_string(const char *string)
 144 {
 145         unsigned int len;
 146
 147         len = strlen(string);
 148         if (len > sizeof(lexer_input_buffer) - 3)
 149                 len = sizeof(lexer_input_buffer) - 3;
 150
 151         strncpy(lexer_input_buffer, string, len);
 152         lexer_input_buffer[len] = '\0';
 153         lexer_input_buffer[len + 1] = '\0';  /* lex/yacc want string double null terminated! */
 154         lexer_read_offset = 0;
 155 }
 156
 157 int evaluate_arithmetic_expression(const char *buffer, long long *ival, double *dval)
 158 {
 159         int rc, bye = 0, has_error = 0;
 160
 161         setup_to_parse_string(buffer);
 162         rc = yyparse(ival, dval, &has_error, &bye);
 163         yyrestart(NULL);
 164         if (rc || bye || has_error) {
 165                 *ival = 0;
 166                 *dval = 0;
 167                 has_error = 1;
 168         }
 169         return has_error;
 170 }
 171
 172 int yyerror(__attribute__((unused)) long long *result,
 173                 __attribute__((unused)) double *dresult,
 174                 __attribute__((unused)) int *has_error,
 175                 __attribute__((unused)) int *bye, const char *msg)
 176 {
 177         fprintf(stderr, "%s\n", msg);
 178         return 0;
 179 }
 180