from itertools import count, chain, tee, islice, cycle from fractions import Fraction # infinite polynomial class class Poly: def __init__(self, gen = None): self.gen, self.source = (None, gen) if type(gen) is Poly \ else (gen, None) def __iter__(self): # We're essentially tee'ing it everytime the iterator # is, well, iterated. This may be excessive. return Poly(self) def getsource(self): if self.gen == None: s = self.source s.getsource() (a,b) = tee(s.gen, 2) s.gen = a self.gen = b def next(self): self.getsource() return next(self.gen) __next__ = next # Overload "<<" as stream input operator. Hey, C++ does it. def __lshift__(self, a): self.gen = a # The other operators are pretty much what one would expect def __neg__(self): return Poly(-x for x in self) def __sub__(a, b): return a + (-b) def __rsub__(a, n): a = Poly(a) def gen(): yield(n - next(a)) for x in a: yield(-x) return Poly(gen()) def __add__(a, b): if type(b) is Poly: return Poly(x + y for (x,y) in zip(a,b)) a = Poly(a) def gen(): yield(next(a) + b) for x in a: yield(x) return Poly(gen()) def __radd__(a,b): return a + b def __mul__(a,b): if not type(b) is Poly: return Poly(x*b for x in a) def gen(): s = Poly(cycle([0])) for y in b: s += y*a yield(next(s)) return Poly(gen()) def __rmul__(a,b): return a*b def __truediv__(a,b): if not type(b) is Poly: return Poly(Fraction(x, b) for x in a) a, b = Poly(a), Poly(b) def gen(): r, bb = a,next(b) while True: aa = next(r) q = Fraction(aa, bb) yield(q) r -= q*b return Poly(gen()) # these two would probably be better as class methods def inte(a): def gen(): yield(0) for (x,n) in zip(a, count(1)): yield(Fraction(x,n)) return Poly(gen()) def diff(a): def gen(): for (x, n) in zip(a, count(0)): if n: yield(x*n) return Poly(gen()) # all that for the syntactic sugar sinx, cosx, tanx, expx = Poly(), Poly(), Poly(), Poly() sinx << inte(cosx) cosx << 1 - inte(sinx) tanx << sinx / cosx # "=" would also work here expx << 1 + inte(expx) for n,x in zip(("sin", "cos", "tan", "exp"), (sinx, cosx, tanx, expx)): print(n, ', '.join(map(str, list(islice(x, 10)))))