# safe_eval.py

"""
This module is an integeral part of the program
MMA - Musical Midi Accompaniment.

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 2 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, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

Bob van der Poel <bob@mellowood.ca>

"""

import re
from math import *

from common import error

safeCmds = [ 'ceil', 'fabs', 'floor', 'exp', 'log', 'log10', 'pow',
             'sqrt', 'acos', 'asin', 'atan', 'atan2', 'cos', 'hypot',
             'sin',  'tan',  'degrees', 'radians', 'cosh', 'sinh',
	     'int', 'in', '.join',   'str', '.split', 'for' ]

def safe_eval( expr ):
        
	toks = re.split( r'([a-zA-Z_\.]+|.)', expr )
	
	for t in toks:
            if len(t)>1 and t not in safeCmds:
                error("Illegal/Unknown operator '%s' in $()." % t)
        try:
            return eval(expr)
        except:
            error("Illegal operation in '%s'." % expr)