font-Roboto/third_party/spiro/curves/numintsynth.py

# Synthesize a procedure to numerically integrate the 3rd order poly spiral

tex = False

if tex:
    mulsym = ' '
else:
    mulsym = ' * '

class Poly:
    def __init__(self, p0, coeffs):
        self.p0 = p0
        self.coeffs = coeffs
    def eval(self, x):
        y = x ** self.p0
        z = 0
        for c in coeffs:
            z += y * c
            y *= x
        return z

def add(poly0, poly1, nmax):
    lp0 = len(poly0.coeffs)
    lp1 = len(poly1.coeffs)
    p0 = min(poly0.p0, poly1.p0)
    n = min(max(poly0.p0 + lp0, poly1.p1 + lp1), nmax) - p0
    if n <= 0: return Poly(0, [])
    coeffs = []
    for i in range(n):
        c = 0
        if i >= poly0.p0 - p0 and i < lp0 + poly0.p0 - p0:
            c += poly0.coeffs[i + p0 - poly0.p0]
        if i >= poly1.p0 - p0 and i < lp1 + poly1.p0 - p0:
            c += poly1.coeffs[i + p0 - poly1.p0]
        coeffs.append(c)
    return Poly(p0, coeffs)

def pr(str):
    if tex:
        print str, '\\\\'
    else:
        print '\t' + str + ';'

def prd(str):
    if tex:
        print str, '\\\\'
    else:
        print '\tdouble ' + str + ';'

def polymul(p0, p1, degree, basename, suppress_odd = False):
    result = []
    for i in range(min(degree, len(p0) + len(p1) - 1)):
        terms = []
        for j in range(i + 1):
            if j < len(p0) and i - j < len(p1):
                t0 = p0[j]
                t1 = p1[i - j]
                if t0 != None and t1 != None:
                    terms.append(t0 + mulsym + t1)
        if terms == []:
            result.append(None)
        else:
            var = basename % i
            if (j % 2 == 0) or not suppress_odd:
                prd(var + ' = ' + ' + '.join(terms))
            result.append(var)
    return result

def polysquare(p0, degree, basename):
    result = []
    for i in range(min(degree, 2 * len(p0) - 1)):
        terms = []
        for j in range((i + 1)/ 2):
            if i - j < len(p0):
                t0 = p0[j]
                t1 = p0[i - j]
                if t0 != None and t1 != None:
                    terms.append(t0 + mulsym + t1)
        if len(terms) >= 1:
            if tex and len(terms) == 1:
                terms = ['2 ' + terms[0]]
            else:
                terms = ['2' + mulsym + '(' + ' + '.join(terms) + ')']
        if (i % 2) == 0:
            t = p0[i / 2]
            if t != None:
                if tex:
                    terms.append(t + '^2')
                else:
                    terms.append(t + mulsym + t)
        if terms == []:
            result.append(None)
        else:
            var = basename % i
            prd(var + ' = ' + ' + '.join(terms))
            result.append(var)
    return result

def mkspiro(degree):
    if tex:
        us = ['u = 1']
        vs = ['v =']
    else:
        us = ['u = 1']
        vs = ['v = 0']
    if tex:
        tp = [None, 't_{11}', 't_{12}', 't_{13}', 't_{14}']
    else:
        tp = [None, 't1_1', 't1_2', 't1_3', 't1_4']
    if tex:
        prd(tp[1] + ' = k_0')
        prd(tp[2] + ' = \\frac{k_1}{2}')
        prd(tp[3] + ' = \\frac{k_2}{6}')
        prd(tp[4] + ' = \\frac{k_3}{24}')
    else:
        prd(tp[1] + ' = km0')
        prd(tp[2] + ' = .5 * km1')
        prd(tp[3] + ' = (1./6) * km2')
        prd(tp[4] + ' = (1./24) * km3')
    tlast = tp
    coef = 1.
    for i in range(1, degree - 1):
        tmp = []
        tcoef = coef
        #print tlast
        for j in range(len(tlast)):
            c = tcoef / (j + 1)
            if (j % 2) == 0 and tlast[j] != None:
                if tex:
                    tmp.append('\\frac{%s}{%.0f}' % (tlast[j], 1./c))
                else:
                    if c < 1e-9:
                        cstr = '%.16e' % c
                    else:
                        cstr = '(1./%d)' % int(.5 + (1./c))
                    tmp.append(cstr + ' * ' + tlast[j])
            tcoef *= .5
        if tmp != []:
            sign = ('+', '-')[(i / 2) % 2]
            var = ('u', 'v')[i % 2]
            if tex:
                if i == 1: pref = ''
                else: pref = sign + ' '
                str = pref + (' ' + sign + ' ').join(tmp)
            else:
                str = var + ' ' + sign + '= ' + ' + '.join(tmp)
            if var == 'u': us.append(str)
            else: vs.append(str)
        if i < degree - 1:
            if tex:
                basename = 't_{%d%%d}' % (i + 1)
            else:
                basename = 't%d_%%d' % (i + 1)
            if i == 1:
                tnext = polysquare(tp, degree - 1, basename)
                t2 = tnext
            elif i == 3:
                tnext = polysquare(t2l, degree - 1, basename)
            elif (i % 2) == 0:
                tnext = polymul(tlast, tp, degree - 1, basename, True)
            else:
                tnext = polymul(t2l, t2, degree - 1, basename)
            t2l = tlast
            tlast = tnext
        coef /= (i + 1)
    if tex:
        pr(' '.join(us))
        pr(' '.join(vs))
    else:
        for u in us:
            pr(u)
        for v in vs:
            pr(v)

if __name__ == '__main__':
    mkspiro(12)