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2.5.2 Grammar Rules for mfcalc

Here are the grammar rules for the multi-function calculator. Most of them are copied directly from calc; three rules, those which mention VAR or FNCT, are new. 

%% /* The grammar follows.  */

input:
  %empty
| input line
;



line:
  '\n'
| exp '\n'   { printf ("%.10g\n", $1); }
| error '\n' { yyerrok;                }
;



exp:
  NUM                { $$ = $1;                         }
| VAR                { $$ = $1->value.var;              }
| VAR '=' exp        { $$ = $3; $1->value.var = $3;     }
| FNCT '(' exp ')'   { $$ = (*($1->value.fnctptr))($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.  */
%%