/* Parser for rpcalc. -*- C -*-
Copyright (C) 1988-1993, 1995, 1998-2015, 2018-2021 Free Software
Foundation, Inc.
This file is part of Bison, the GNU Compiler Compiler.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Reverse Polish Notation calculator. */
%{
#include <stdio.h>
#include <math.h>
int yylex (void);
void yyerror (char const *);
%}
%define api.value.type {double}
%token NUM
%% /* Grammar rules and actions follow. */
input:
%empty
| input line
;
line:
'\n'
| exp '\n' { printf ("%.10g\n", $1); }
;
exp:
NUM
| exp exp '+' { $$ = $1 + $2; }
| exp exp '-' { $$ = $1 - $2; }
| exp exp '*' { $$ = $1 * $2; }
| exp exp '/' { $$ = $1 / $2; }
| exp exp '^' { $$ = pow ($1, $2); } /* Exponentiation */
| exp 'n' { $$ = -$1; } /* Unary minus */
;
%%
/* The lexical analyzer returns a double floating point
number on the stack and the token NUM, or the numeric code
of the character read if not a number. It skips all blanks
and tabs, and returns 0 for end-of-input. */
#include <ctype.h>
#include <stdlib.h>
int
yylex (void)
{
int c = getchar ();
/* Skip white space. */
while (c == ' ' || c == '\t')
c = getchar ();
/* Process numbers. */
if (c == '.' || isdigit (c))
{
ungetc (c, stdin);
if (scanf ("%lf", &yylval) != 1)
abort ();
return NUM;
}
/* Return end-of-input. */
else if (c == EOF)
return YYEOF;
/* Return a single char. */
else
return c;
}
int
main (void)
{
return yyparse ();
}
#include <stdio.h>
/* Called by yyparse on error. */
void
yyerror (char const *s)
{
fprintf (stderr, "%s\n", s);
}
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