%{
  #include <stdio.h>  /* For printf, etc. */
  #include <math.h>   /* For pow, used in the grammar. */
  #include "calc.h"   /* Contains definition of 'symrec'. */
  int yylex (void);
  void yyerror (char const *);
%}
%define api.value.type union /* Generate YYSTYPE from these types: */
%token <double>  NUM     /* Double precision number. */
%token <symrec*> VAR FUN /* Symbol table pointer: variable/function. */
%nterm <double>  exp
%precedence '='
%left '-' '+'
%left '*' '/'
%precedence NEG /* negation--unary minus */
%right '^'      /* exponentiation */
%% /* The grammar follows. */
input:
  %empty
| input line
;
line:
  '\n'
| exp '\n'   { printf ("%.10g\n", $1); }
| error '\n' { yyerrok;                }
;
exp:
  NUM
| VAR                { $$ = $1->value.var;              }
| VAR '=' exp        { $$ = $3; $1->value.var = $3;     }
| FUN '(' exp ')'    { $$ = $1->value.fun ($3);         }
| exp '+' exp        { $$ = $1 + $3;                    }
| exp '-' exp        { $$ = $1 - $3;                    }
| exp '*' exp        { $$ = $1 * $3;                    }
| exp '/' exp        { $$ = $1 / $3;                    }
| '-' exp  %prec NEG { $$ = -$2;                        }
| exp '^' exp        { $$ = pow ($1, $3);               }
| '(' exp ')'        { $$ = $2;                         }
;
/* End of grammar. */
%%