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 %right SUFFIX
  61 %left '*' '/'
  62 %right '^'
  63 %left '%'
  64 %nonassoc UMINUS
  65 %parse-param { long long *result }
  66 %parse-param { double *dresult }
  67 %parse-param { int *has_error }
  68 %parse-param { int *bye }
  69
  70 %type <v> expression
  71 %%
  72
  73 top_level:      expression {
  74                                 *result = $1.ival;
  75                                 *dresult = $1.dval;
  76                                 *has_error = $1.has_error;
  77                         }
  78                 | expression error {
  79                                 *result = $1.ival;
  80                                 *dresult = $1.dval;
  81                                 *has_error = 1;
  82                         }
  83 expression:     expression '+' expression {
  84                         if (!$1.has_dval && !$3.has_dval)
  85                                 $$.ival = $1.ival + $3.ival;
  86                         else
  87                                 $$.ival = (long long) ($1.dval + $3.dval);
  88                         $$.dval = $1.dval + $3.dval;
  89                         $$.has_error = $1.has_error || $3.has_error;
  90                 }
  91         |       expression '-' expression {
  92                         if (!$1.has_dval && !$3.has_dval)
  93                                 $$.ival = $1.ival - $3.ival;
  94                         else
  95                                 $$.ival = (long long) ($1.dval - $3.dval);
  96                         $$.dval = $1.dval - $3.dval;
  97                         $$.has_error = $1.has_error || $3.has_error;
  98                 }
  99         |       expression '*' expression {
 100                         if (!$1.has_dval && !$3.has_dval)
 101                                 $$.ival = $1.ival * $3.ival;
 102                         else
 103                                 $$.ival = (long long) ($1.dval * $3.dval);
 104                         $$.dval = $1.dval * $3.dval;
 105                         $$.has_error = $1.has_error || $3.has_error;
 106                 }
 107         |       expression '/' expression {
 108                         if ($3.ival == 0)
 109                                 yyerror(0, 0, 0, 0, "divide by zero");
 110                         else
 111                                 $$.ival = $1.ival / $3.ival;
 112                         if ($3.dval < 1e-20 && $3.dval > -1e-20)
 113                                 yyerror(0, 0, 0, 0, "divide by zero");
 114                         else
 115                                 $$.dval = $1.dval / $3.dval;
 116                         if ($3.has_dval || $1.has_dval)
 117                                 $$.ival = (long long) $$.dval;
 118                         $$.has_error = $1.has_error || $3.has_error;
 119                 }
 120         |       '-' expression %prec UMINUS {
 121                         $$.ival = -$2.ival;
 122                         $$.dval = -$2.dval;
 123                         $$.has_error = $2.has_error;
 124                 }
 125         |       '(' expression ')' { $$ = $2; }
 126         |       expression SUFFIX {
 127                         if (!$1.has_dval && !$2.has_dval)
 128                                 $$.ival = $1.ival * $2.ival;
 129                         else
 130                                 $$.ival = (long long) $1.dval * $2.dval;
 131                         if ($1.has_dval || $2.has_dval)
 132                                 $$.dval = $1.dval * $2.dval;
 133                         else
 134                                 $$.dval = $1.ival * $2.ival;
 135                         $$.has_error = $1.has_error || $2.has_error;
 136                 }
 137         |       expression '%' expression {
 138                         if ($1.has_dval || $3.has_dval)
 139                                 yyerror(0, 0, 0, 0, "modulo on floats");
 140                         if ($3.ival == 0)
 141                                 yyerror(0, 0, 0, 0, "divide by zero");
 142                         else {
 143                                 $$.ival = $1.ival % $3.ival;
 144                                 $$.dval = $$.ival;
 145                         }
 146                         $$.has_error = $1.has_error || $3.has_error;
 147                 }
 148         |       expression '^' expression {
 149                         $$.has_error = $1.has_error || $3.has_error;
 150                         if (!$1.has_dval && !$3.has_dval) {
 151                                 int i;
 152
 153                                 if ($3.ival == 0) {
 154                                         $$.ival = 1;
 155                                 } else if ($3.ival > 0) {
 156                                         long long tmp = $1.ival;
 157                                         $$.ival = 1.0;
 158                                         for (i = 0; i < $3.ival; i++)
 159                                                 $$.ival *= tmp;
 160                                 }  else {
 161                                         /* integers, 2^-3, ok, we now have doubles */
 162                                         double tmp;
 163                                         if ($1.ival == 0 && $3.ival == 0) {
 164                                                 tmp = 1.0;
 165                                                 $$.has_error = 1;
 166                                         } else {
 167                                                 double x = (double) $1.ival;
 168                                                 double y = (double) $3.ival;
 169                                                 tmp = pow(x, y);
 170                                         }
 171                                         $$.ival = (long long) tmp;
 172                                 }
 173                                 $$.dval = pow($1.dval, $3.dval);
 174                         } else {
 175                                 $$.dval = pow($1.dval, $3.dval);
 176                                 $$.ival = (long long) $$.dval;
 177                         }
 178                 }
 179         |       NUMBER { $$ = $1; }
 180         |       BYE { $$ = $1; *bye = 1; };
 181 %%
 182 #include <stdio.h>
 183
 184 /* Urgh.  yacc and lex are kind of horrible.  This is not thread safe, obviously. */
 185 static int lexer_read_offset = 0;
 186 static char lexer_input_buffer[1000];
 187
 188 int lexer_input(char* buffer, int *bytes_read, int bytes_requested)
 189 {
 190         int bytes_left = strlen(lexer_input_buffer) - lexer_read_offset;
 191
 192         if (bytes_requested > bytes_left )
 193                 bytes_requested = bytes_left;
 194         memcpy(buffer, &lexer_input_buffer[lexer_read_offset], bytes_requested);
 195         *bytes_read = bytes_requested;
 196         lexer_read_offset += bytes_requested;
 197         return 0;
 198 }
 199
 200 static void setup_to_parse_string(const char *string)
 201 {
 202         unsigned int len;
 203
 204         len = strlen(string);
 205         if (len > sizeof(lexer_input_buffer) - 3)
 206                 len = sizeof(lexer_input_buffer) - 3;
 207
 208         strncpy(lexer_input_buffer, string, len);
 209         lexer_input_buffer[len] = '\0';
 210         lexer_input_buffer[len + 1] = '\0';  /* lex/yacc want string double null terminated! */
 211         lexer_read_offset = 0;
 212 }
 213
 214 int evaluate_arithmetic_expression(const char *buffer, long long *ival, double *dval)
 215 {
 216         int rc, bye = 0, has_error = 0;
 217
 218         setup_to_parse_string(buffer);
 219         rc = yyparse(ival, dval, &has_error, &bye);
 220         yyrestart(NULL);
 221         if (rc || bye || has_error) {
 222                 *ival = 0;
 223                 *dval = 0;
 224                 has_error = 1;
 225         }
 226         return has_error;
 227 }
 228
 229 int yyerror(__attribute__((unused)) long long *result,
 230                 __attribute__((unused)) double *dresult,
 231                 __attribute__((unused)) int *has_error,
 232                 __attribute__((unused)) int *bye,
 233                 __attribute__((unused)) const char *msg)
 234 {
 235         /* We do not need to do anything here. */
 236         return 0;
 237 }
 238