transforms.py 文件源码

def _fourier_transform(f, x, k, a, b, name, simplify=True):
    """
    Compute a general Fourier-type transform
        F(k) = a int_-oo^oo exp(b*I*x*k) f(x) dx.

    For suitable choice of a and b, this reduces to the standard Fourier
    and inverse Fourier transforms.
    """
    from sympy import exp, I, oo
    F = integrate(a*f*exp(b*I*x*k), (x, -oo, oo))

    if not F.has(Integral):
        return _simplify(F, simplify), True

    if not F.is_Piecewise:
        raise IntegralTransformError(name, f, 'could not compute integral')

    F, cond = F.args[0]
    if F.has(Integral):
        raise IntegralTransformError(name, f, 'integral in unexpected form')

    return _simplify(F, simplify), cond