Kelvie Wong

#!/usr/bin/python
""" fold_constants.py
    Kelvie Wong
    February 28, 2006

    Generates C code where the constants are folded (stupid C doesn't do it
    itself, because a function call to pow or sqrt is too complex for a
    constant expression).  Spits it all out to stdout, so pipe away."""


# TODO: arrays
# TODO: work on more than just floats?
# TODO: comments
import re, os, sys
from math import *

M_PI = pi
M_2_PI = 2/pi
M_PI_2 = pi/2

if __name__ == '__main__':
    file =  open(sys.argv[1])
    expression = ''
    prefix = ''
    suffix = ''
    vardict = {} # A dictionary to hold the variables needed by each other
    for line in file:
        # Find the assignment operator!
        where = line.find('=')+1

        # If there is an assignment operator or if this is a continued line
        if where or expression:
            # For now, ignore array declarations
            if line.find('{') is not -1: # i.e. if it is found
                print line.strip('\n')
                continue

            # What about comments?
            # TODO: Eat comments, and place them on a separate line after (or
            # inline? depending on how many cols left in the line)
            #if line.find('/*') is not -1 and line.find('/*') < line.find('='):
                # if the first assignment operator is commented...
                #nextcomment = line.find('*/')

            # No semicolon means that the expression continues on to the next
            # line.
            where2 = line.find(';')
            if where2 is not -1: # is found
                expression += line[where:where2]
                newvalue = str(eval(expression, globals(), vardict))

                # If there's a previous prefix (i.e. this is a continued line),
                # use it, otherwise grab the prefix, prefix being the
                # assignment expression.  Same goes for the suffix.
                prefix = prefix or line[0:where]
                suffix = suffix or line[where2:-1]

                # Output, as well, store the variable in the Python namespace;
                # in case the variables are used later.
                print '%s %s%s' % (prefix, newvalue, suffix)
                varname = prefix.replace('const ', '')
                varname = varname.replace('float ', '')
                varname = varname.replace('static ', '')
                varname = varname.strip('= \t')
                vardict[varname] = float(newvalue)
                prefix = ''
                expression = ''
                suffix = ''
            else:
                # Save the (incomplete) expression for later.
                expression += line[where:line.rfind('\n')]
                if not prefix:
                    prefix = line[0:where]
                if not suffix:
                    suffix = line[where2:-1]

        # If there isn't an assignment operator, just print the line.
        else:
            # print produces a newline anyways.
            print line.strip('\n')