Globals.py

#!/usr/bin/python3

#  Globals.py
#
#  Copyright (C) 2015 Caian Benedicto <caianbene@gmail.com>
#
#  This file is part of Asparagus
#
#  Asparagus 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, or (at your option)
#  any later version.
#
#  Asparagus 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.
#

import sympy
from sympy.parsing.sympy_parser import parse_expr

def time(symbols): 
    return symbols.getSymbol('$global', 'time', nonnegative=True)

time_alias = 't'

def gravity(symbols): 
    return (
        symbols.getSymbol('$global', 'gravity.value', nonnegative=True),
        symbols.getSymbol('$global', 'gravity.theta')
    )

gravity_alias = 'g'

def isTimeConstant(s, symbols):
    s = sympy.simplify(s)
    if s == time(symbols):
        return False
    args = s.args
    for arg in args:
        if not isTimeConstant(arg, symbols):
            return False
    return True

def convertAttachment(att, mode = 't'):
    m = att[2]
    if mode == m:
        return (att[0], att[1], att[2])
    elif mode == 'r':
        if m == 'p':
            d = att[0]
            t = att[1]
            return (d*sympy.sin(t), d*sympy.cos(t), mode)
        else:
            raise Exception('invalid attachment mode %s' % str(m))
    elif mode == 'p':
        if m == 'r':
            x = att[0]
            y = att[1]
            # TODO remember to flip y during c->r
            # check theta direction
            return (sympy.sqrt(x**2+y**2), sympy.atan2(x, y), mode)
        else:
            raise Exception('invalid attachment mode %s' % str(m))
    else:
        raise Exception('invalid attachment mode %s' % str(mode))

def positify(expr, symbag):
    if expr.is_Symbol:
        symbag[expr] = sympy.Symbol(expr.name, positive=True)
    else:
        for arg in expr.args:
            positify(arg, symbag)

def parseExpr(expr):
    if expr[0] == '"' and expr[-1] == '"':
        expr = expr[1:-1]
    symbag = {}
    expr = parse_expr(expr)
    positify(expr, symbag)
    expr = expr.subs(symbag)
    return expr

def no_alias(t):
    return t

def getObjName(name):
    return name

def getAttachProp(objname, prop):
    return 'attach.%s.%s' % (objname, prop)

def getPropString(objname, prop):
    return '%s.%s' % (objname, prop)

def norm2d(a):
    return sympy.simplify(sympy.sqrt(a[0]**2+a[1]**2))

def cross2d(a, b):
    return sympy.simplify(a[0]*b[1]-b[0]*a[1])

def dot2d(a, b):
    return sympy.simplify(a[0]*b[0]+a[1]*b[1])

def ssign(a):
    return sympy.simplify(sympy.sign(a))