# liangbarsky incorrect

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Issue #101
new

When called with the following arguments:

liangbarsky(-0.25, 2.25, 1.25, 0.75, 0.5, 2.5, 0.5, 0.5)

I expect the line to intersect the box, however `None, None, None, None`

is returned. I'm not totally sure where the bug is, for my needs all i wanted was a boolean yes or no to if the line intersected the box. I modified your code and made some changes based on outside resources and this is what I came up with:

dx = x2 - x1 * 1.0 dy = y2 - y1 * 1.0 t0 = 0.0 t1 = 1.0 checks = ((-dx, -(left - x1)), ( dx, right - x1), (-dy, -(bottom - y1)), ( dy, top - y1)) for p, q in checks: if p == 0 and q < 0: return False if p != 0: r = q / (p * 1.0) if p < 0: if r > t1: return False elif r > t0: t0 = r else: if r < t0: return False elif r < t1: t1 = r return True

I reproduced the algorithm from the C code from http://www.skytopia.com/project/articles/compsci/clipping.html#alg