external/bsd/flex/dist/examples/manual/front.y

   1 /* C code supplied at the beginning of the file.  */
   2
   3 %{
   4
   5 #include <stdio.h>
   6 #include <string.h>
   7
   8 extern int  yylexlinenum;                   /* these are in YYlex      */
   9 extern char *yytext;                        /* current token           */
  10
  11
  12 %}
  13
  14 /* Keywords and reserved words begin here.  */
  15
  16 %union{                                     /* this is the data union  */
  17     char   name[128];                       /* names                   */
  18 }
  19
  20 /*-------------------- the reserved words -----------------------------*/
  21
  22 %token PERIOD
  23 %token NEWLINE
  24 %token POSITIONAL
  25
  26 %token VERB
  27 %token ADVERB
  28
  29 %token PROPER_NOUN
  30 %token NOUN
  31
  32 %token DECLARATIVE
  33 %token CONDITIONAL
  34
  35
  36 %type  <name> declarative
  37 %type  <name> verb_phrase
  38 %type  <name> noun_phrase
  39 %type  <name> position_phrase
  40 %type  <name> adverb
  41
  42 %type  <name> POSITIONAL VERB ADVERB PROPER_NOUN
  43 %type  <name> NOUN DECLARATIVE CONDITIONAL
  44
  45 %%
  46
  47 sentence_list : sentence
  48               | sentence_list NEWLINE sentence
  49               ;
  50
  51
  52 sentence : verb_phrase noun_phrase position_phrase adverb period
  53            {
  54              printf("I understand that sentence.\n");
  55              printf("VP = %s \n",$1);
  56              printf("NP = %s \n",$2);
  57              printf("PP = %s \n",$3);
  58              printf("AD = %s \n",$4);
  59            }
  60          | { yyerror("That's a strange sentence !!");  }
  61          ;
  62
  63 position_phrase : POSITIONAL  declarative PROPER_NOUN
  64                   {
  65                     sprintf($$,"%s %s %s",$1,$2,$3);
  66                   }
  67                 | /* empty */ { strcpy($$,""); }
  68                 ;
  69
  70
  71 verb_phrase : VERB { strcpy($$,$1); strcat($$," "); }
  72             | adverb VERB
  73               {
  74                 sprintf($$,"%s %s",$1,$2);
  75               }
  76             ;
  77
  78 adverb : ADVERB      { strcpy($$,$1); }
  79        | /* empty */ { strcpy($$,""); }
  80        ;
  81
  82 noun_phrase : DECLARATIVE NOUN
  83               {
  84                 sprintf($$,"%s %s",$1,$2);
  85               }
  86             | CONDITIONAL declarative NOUN
  87                   {
  88                     sprintf($$,"%s %s %s",$1,$2,$3);
  89                   }
  90             | NOUN { strcpy($$,$1); strcat($$," "); }
  91             ;
  92
  93 declarative : DECLARATIVE { strcpy($$,$1); }
  94             | /* empty */ { strcpy($$,""); }
  95             ;
  96
  97 period : /* empty */
  98        | PERIOD
  99        ;
 100
 101
 102 %%
 103
 104 /* Supplied main() and yyerror() functions.  */
 105
 106 int main(int argc, char *argv[])
 107 {
 108   yyparse();   /* parse the file          */
 109   return(0);
 110 }
 111
 112 int yyerror(char *message)
 113 {
 114   extern FILE *yyout;
 115
 116   fprintf(yyout,"\nError at line %5d. (%s) \n",
 117                      yylexlinenum,message);
 118 }