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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  *
  19  */
  20
  21 #include <stdio.h>
  22 #include <string.h>
  23 #include <math.h>
  24
  25 struct parser_value_type {
  26         double dval;
  27         long long ival;
  28         int has_dval;
  29         int has_error;
  30 };
  31
  32 typedef union valtype {
  33         struct parser_value_type v;
  34 } PARSER_VALUE_TYPE;
  35
  36 #define YYSTYPE PARSER_VALUE_TYPE
  37
  38 int yyerror(__attribute__((unused)) long long *result,
  39                 __attribute__((unused)) double *dresult,
  40                 __attribute__((unused)) int *has_error,
  41                 __attribute__((unused)) int *units_specified,
  42                 __attribute__((unused)) const char *msg);
  43
  44 extern int yylex(void);
  45 extern void yyrestart(FILE *file);
  46 extern int lexer_value_is_time;
  47
  48 %}
  49
  50 %union valtype {
  51         struct parser_value_type {
  52                 double dval;
  53                 long long ival;
  54                 int has_dval;
  55                 int has_error;
  56         } v;
  57 };
  58
  59 %token <v> NUMBER
  60 %token <v> BYE
  61 %token <v> SUFFIX
  62 %left '-' '+'
  63 %right SUFFIX
  64 %left '*' '/'
  65 %right '^'
  66 %left '%'
  67 %nonassoc UMINUS
  68 %parse-param { long long *result }
  69 %parse-param { double *dresult }
  70 %parse-param { int *has_error }
  71 %parse-param { int *units_specified }
  72
  73 %type <v> expression
  74 %%
  75
  76 top_level:      expression {
  77                                 *result = $1.ival;
  78                                 *dresult = $1.dval;
  79                                 *has_error = $1.has_error;
  80                         }
  81                 | expression error {
  82                                 *result = $1.ival;
  83                                 *dresult = $1.dval;
  84                                 *has_error = 1;
  85                         }
  86 expression:     expression '+' expression {
  87                         if (!$1.has_dval && !$3.has_dval)
  88                                 $$.ival = $1.ival + $3.ival;
  89                         else
  90                                 $$.ival = (long long) ($1.dval + $3.dval);
  91                         $$.dval = $1.dval + $3.dval;
  92                         $$.has_error = $1.has_error || $3.has_error;
  93                 }
  94         |       expression '-' expression {
  95                         if (!$1.has_dval && !$3.has_dval)
  96                                 $$.ival = $1.ival - $3.ival;
  97                         else
  98                                 $$.ival = (long long) ($1.dval - $3.dval);
  99                         $$.dval = $1.dval - $3.dval;
 100                         $$.has_error = $1.has_error || $3.has_error;
 101                 }
 102         |       expression '*' expression {
 103                         if (!$1.has_dval && !$3.has_dval)
 104                                 $$.ival = $1.ival * $3.ival;
 105                         else
 106                                 $$.ival = (long long) ($1.dval * $3.dval);
 107                         $$.dval = $1.dval * $3.dval;
 108                         $$.has_error = $1.has_error || $3.has_error;
 109                 }
 110         |       expression '/' expression {
 111                         if ($3.ival == 0)
 112                                 yyerror(0, 0, 0, 0, "divide by zero");
 113                         else
 114                                 $$.ival = $1.ival / $3.ival;
 115                         if ($3.dval < 1e-20 && $3.dval > -1e-20)
 116                                 yyerror(0, 0, 0, 0, "divide by zero");
 117                         else
 118                                 $$.dval = $1.dval / $3.dval;
 119                         if ($3.has_dval || $1.has_dval)
 120                                 $$.ival = (long long) $$.dval;
 121                         $$.has_error = $1.has_error || $3.has_error;
 122                 }
 123         |       '-' expression %prec UMINUS {
 124                         $$.ival = -$2.ival;
 125                         $$.dval = -$2.dval;
 126                         $$.has_error = $2.has_error;
 127                 }
 128         |       '(' expression ')' { $$ = $2; }
 129         |       expression SUFFIX {
 130                         if (!$1.has_dval && !$2.has_dval)
 131                                 $$.ival = $1.ival * $2.ival;
 132                         else
 133                                 $$.ival = (long long) $1.dval * $2.dval;
 134                         if ($1.has_dval || $2.has_dval)
 135                                 $$.dval = $1.dval * $2.dval;
 136                         else
 137                                 $$.dval = $1.ival * $2.ival;
 138                         $$.has_error = $1.has_error || $2.has_error;
 139                         *units_specified = 1;
 140                 }
 141         |       expression '%' expression {
 142                         if ($1.has_dval || $3.has_dval)
 143                                 yyerror(0, 0, 0, 0, "modulo on floats");
 144                         if ($3.ival == 0)
 145                                 yyerror(0, 0, 0, 0, "divide by zero");
 146                         else {
 147                                 $$.ival = $1.ival % $3.ival;
 148                                 $$.dval = $$.ival;
 149                         }
 150                         $$.has_error = $1.has_error || $3.has_error;
 151                 }
 152         |       expression '^' expression {
 153                         $$.has_error = $1.has_error || $3.has_error;
 154                         if (!$1.has_dval && !$3.has_dval) {
 155                                 int i;
 156
 157                                 if ($3.ival == 0) {
 158                                         $$.ival = 1;
 159                                 } else if ($3.ival > 0) {
 160                                         long long tmp = $1.ival;
 161                                         $$.ival = 1.0;
 162                                         for (i = 0; i < $3.ival; i++)
 163                                                 $$.ival *= tmp;
 164                                 }  else {
 165                                         /* integers, 2^-3, ok, we now have doubles */
 166                                         double tmp;
 167                                         if ($1.ival == 0 && $3.ival == 0) {
 168                                                 tmp = 1.0;
 169                                                 $$.has_error = 1;
 170                                         } else {
 171                                                 double x = (double) $1.ival;
 172                                                 double y = (double) $3.ival;
 173                                                 tmp = pow(x, y);
 174                                         }
 175                                         $$.ival = (long long) tmp;
 176                                 }
 177                                 $$.dval = pow($1.dval, $3.dval);
 178                         } else {
 179                                 $$.dval = pow($1.dval, $3.dval);
 180                                 $$.ival = (long long) $$.dval;
 181                         }
 182                 }
 183         |       NUMBER { $$ = $1; };
 184 %%
 185 #include <stdio.h>
 186
 187 /* Urgh.  yacc and lex are kind of horrible.  This is not thread safe, obviously. */
 188 static int lexer_read_offset = 0;
 189 static char lexer_input_buffer[1000];
 190
 191 int lexer_input(char* buffer, unsigned int *bytes_read, int bytes_requested)
 192 {
 193         int bytes_left = strlen(lexer_input_buffer) - lexer_read_offset;
 194
 195         if (bytes_requested > bytes_left )
 196                 bytes_requested = bytes_left;
 197         memcpy(buffer, &lexer_input_buffer[lexer_read_offset], bytes_requested);
 198         *bytes_read = bytes_requested;
 199         lexer_read_offset += bytes_requested;
 200         return 0;
 201 }
 202
 203 static void setup_to_parse_string(const char *string)
 204 {
 205         unsigned int len;
 206
 207         len = sizeof(lexer_input_buffer) - 3;
 208         if (len > strlen(string))
 209                 len = strlen(string);
 210
 211         strncpy(lexer_input_buffer, string, len);
 212         lexer_input_buffer[len] = '\0';
 213         lexer_input_buffer[len + 1] = '\0';  /* lex/yacc want string double null terminated! */
 214         lexer_read_offset = 0;
 215 }
 216
 217 int evaluate_arithmetic_expression(const char *buffer, long long *ival, double *dval,
 218                                         double implied_units, int is_time)
 219 {
 220         int rc, units_specified = 0, has_error = 0;
 221
 222         lexer_value_is_time = is_time;
 223         setup_to_parse_string(buffer);
 224         rc = yyparse(ival, dval, &has_error, &units_specified);
 225         yyrestart(NULL);
 226         if (rc || has_error) {
 227                 *ival = 0;
 228                 *dval = 0;
 229                 has_error = 1;
 230         }
 231         if (!units_specified) {
 232                 *ival = (int) ((double) *ival * implied_units);
 233                 *dval = *dval * implied_units;
 234         }
 235         return has_error;
 236 }
 237
 238 int yyerror(__attribute__((unused)) long long *result,
 239                 __attribute__((unused)) double *dresult,
 240                 __attribute__((unused)) int *has_error,
 241                 __attribute__((unused)) int *units_specified,
 242                 __attribute__((unused)) const char *msg)
 243 {
 244         /* We do not need to do anything here. */
 245         return 0;
 246 }
 247