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7 lines
208 B
Python
7 lines
208 B
Python
def lb_exact(n):
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"""Returns `log2(n)`, raising if `n` is not a power of 2."""
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lb = n.bit_length() - 1
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if lb < 0 or n != 1 << lb:
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raise ValueError(f"{n} is not a power of 2")
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return lb
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