%{
/*
 * Example 1-7: Simple yacc sentence parser ch1-05.byacc
 *
 * A lexer for the basic grammer to use for recognizing English sentences.
 */
#include <stdio.h>
%}

%token NOUN PRONOUN VERB ADVERB ADJECTIVE PREPOSITION CONJUNCTION

%%

sentence: subject VERB object { printf("Sentence is valid.\n"); }
    ;

subject:    NOUN
    |       PRONOUN
    ;

object:     NOUN
    ;

%%

extern FILE *yyin;

main()
{
    while(!feof(yyin)) {
        yyparse();
    }
}

yyerror(s)
char *s;
{
    fprintf(stderr, "%s\n", s);
}