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 #include <math.h>
  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 %token <v> SUFFIX
  59 %left '-' '+'
  60 %left '*' '/'
  61 %right '^'
  62 %left '%'
  63 %nonassoc UMINUS
  64 %parse-param { long long *result }
  65 %parse-param { double *dresult }
  66 %parse-param { int *has_error }
  67 %parse-param { int *bye }
  68
  69 %type <v> expression
  70 %%
  71
  72 top_level:      expression {
  73                                 *result = $1.ival;
  74                                 *dresult = $1.dval;
  75                                 *has_error = $1.has_error;
  76                         }
  77                 | expression error {
  78                                 *result = $1.ival;
  79                                 *dresult = $1.dval;
  80                                 *has_error = 1;
  81                         }
  82 expression:     expression '+' expression {
  83                         if (!$1.has_dval && !$3.has_dval)
  84                                 $$.ival = $1.ival + $3.ival;
  85                         else
  86                                 $$.ival = (long long) ($1.dval + $3.dval);
  87                         $$.dval = $1.dval + $3.dval;
  88                         $$.has_error = $1.has_error || $3.has_error;
  89                 }
  90         |       expression '-' expression {
  91                         if (!$1.has_dval && !$3.has_dval)
  92                                 $$.ival = $1.ival - $3.ival;
  93                         else
  94                                 $$.ival = (long long) ($1.dval - $3.dval);
  95                         $$.dval = $1.dval - $3.dval;
  96                         $$.has_error = $1.has_error || $3.has_error;
  97                 }
  98         |       expression '*' expression {
  99                         if (!$1.has_dval && !$3.has_dval)
 100                                 $$.ival = $1.ival * $3.ival;
 101                         else
 102                                 $$.ival = (long long) ($1.dval * $3.dval);
 103                         $$.dval = $1.dval * $3.dval;
 104                         $$.has_error = $1.has_error || $3.has_error;
 105                 }
 106         |       expression '/' expression {
 107                         if ($3.ival == 0)
 108                                 yyerror(0, 0, 0, 0, "divide by zero");
 109                         else
 110                                 $$.ival = $1.ival / $3.ival;
 111                         if ($3.dval < 1e-20 && $3.dval > -1e-20)
 112                                 yyerror(0, 0, 0, 0, "divide by zero");
 113                         else
 114                                 $$.dval = $1.dval / $3.dval;
 115                         if ($3.has_dval || $1.has_dval)
 116                                 $$.ival = (long long) $$.dval;
 117                         $$.has_error = $1.has_error || $3.has_error;
 118                 }
 119         |       '-' expression %prec UMINUS {
 120                         $$.ival = -$2.ival;
 121                         $$.dval = -$2.dval;
 122                         $$.has_error = $2.has_error;
 123                 }
 124         |       '(' expression ')' { $$ = $2; }
 125         |       expression SUFFIX {
 126                         if (!$1.has_dval && !$2.has_dval)
 127                                 $$.ival = $1.ival * $2.ival;
 128                         else
 129                                 $$.ival = (long long) $1.dval * $2.dval;
 130                         if ($1.has_dval || $2.has_dval)
 131                                 $$.dval = $1.dval * $2.dval;
 132                         else
 133                                 $$.dval = $1.ival * $2.ival;
 134                         $$.has_error = $1.has_error || $2.has_error;
 135                 }
 136         |       expression '%' expression {
 137                         if ($1.has_dval || $3.has_dval)
 138                                 yyerror(0, 0, 0, 0, "modulo on floats");
 139                         if ($3.ival == 0)
 140                                 yyerror(0, 0, 0, 0, "divide by zero");
 141                         else
 142                                 $$.ival = $1.ival % $3.ival;
 143                         $$.has_error = $1.has_error || $3.has_error;
 144                 }
 145         |       expression '^' expression {
 146                         $$.has_error = $1.has_error || $3.has_error;
 147                         if (!$1.has_dval && !$3.has_dval) {
 148                                 int i;
 149
 150                                 if ($3.ival == 0) {
 151                                         $$.ival = 1;
 152                                 } else if ($3.ival > 0) {
 153                                         long long tmp = $1.ival;
 154                                         $$.ival = 1.0;
 155                                         for (i = 0; i < $3.ival; i++)
 156                                                 $$.ival *= tmp;
 157                                 }  else {
 158                                         /* integers, 2^-3, ok, we now have doubles */
 159                                         double tmp;
 160                                         if ($1.ival == 0 && $3.ival == 0) {
 161                                                 tmp = 1.0;
 162                                                 $$.has_error = 1;
 163                                         } else {
 164                                                 tmp = pow((double) $1.ival,
 165                                                                 (double) $3.ival);
 166                                         }
 167                                         $$.ival = (long long) tmp;
 168                                 }
 169                                 $$.dval = pow($1.dval, $3.dval);
 170                         } else {
 171                                 $$.dval = pow($1.dval, $3.dval);
 172                                 $$.ival = (long long) $$.dval;
 173                         }
 174                 }
 175         |       NUMBER { $$ = $1; }
 176         |       BYE { $$ = $1; *bye = 1; };
 177 %%
 178 #include <stdio.h>
 179
 180 /* Urgh.  yacc and lex are kind of horrible.  This is not thread safe, obviously. */
 181 static int lexer_read_offset = 0;
 182 static char lexer_input_buffer[1000];
 183
 184 int lexer_input(char* buffer, int *bytes_read, int bytes_requested)
 185 {
 186         int bytes_left = strlen(lexer_input_buffer) - lexer_read_offset;
 187
 188         if (bytes_requested > bytes_left )
 189                 bytes_requested = bytes_left;
 190         memcpy(buffer, &lexer_input_buffer[lexer_read_offset], bytes_requested);
 191         *bytes_read = bytes_requested;
 192         lexer_read_offset += bytes_requested;
 193         return 0;
 194 }
 195
 196 static void setup_to_parse_string(const char *string)
 197 {
 198         unsigned int len;
 199
 200         len = strlen(string);
 201         if (len > sizeof(lexer_input_buffer) - 3)
 202                 len = sizeof(lexer_input_buffer) - 3;
 203
 204         strncpy(lexer_input_buffer, string, len);
 205         lexer_input_buffer[len] = '\0';
 206         lexer_input_buffer[len + 1] = '\0';  /* lex/yacc want string double null terminated! */
 207         lexer_read_offset = 0;
 208 }
 209
 210 int evaluate_arithmetic_expression(const char *buffer, long long *ival, double *dval)
 211 {
 212         int rc, bye = 0, has_error = 0;
 213
 214         setup_to_parse_string(buffer);
 215         rc = yyparse(ival, dval, &has_error, &bye);
 216         yyrestart(NULL);
 217         if (rc || bye || has_error) {
 218                 *ival = 0;
 219                 *dval = 0;
 220                 has_error = 1;
 221         }
 222         return has_error;
 223 }
 224
 225 int yyerror(__attribute__((unused)) long long *result,
 226                 __attribute__((unused)) double *dresult,
 227                 __attribute__((unused)) int *has_error,
 228                 __attribute__((unused)) int *bye, const char *msg)
 229 {
 230         fprintf(stderr, "%s\n", msg);
 231         return 0;
 232 }
 233