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