Python method for encoding Boolean functions

Question

I know that given n inputs, there are 2^(2^n) possible Boolean functions. Is there some way in Python of encoding these functions, so that when, say, given a number between 0 and 65,535 and four Boolean values, I can get a corresponding Boolean value returned?

Boojum · Accepted Answer · 2015-05-22 06:14:04Z

2

Use the bits of N as a truth-table, and then use the inputs to select a bit in it:

def boolFunc(N, *args):
    bit = 0
    for value in args:
        bit = 2 * bit + int(value)
    return N & (1 << bit) != 0

For example, with 4 bits of input, 27030 is the parity function:

>>> boolFunc( 27030, False, False, False, False )
False
>>> boolFunc( 27030, False, True, False, False )
True
>>> boolFunc( 27030, False, True, False, True )
False
>>> boolFunc( 27030, True, True, True, False )
True

For 5 bits, the parity function is 2523490710:

>>> boolFunc( 2523490710, True, False, True, False, True )
True

edited May 22, 2015 at 6:14

answered May 21, 2015 at 23:35

Boojum

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3 Comments

Melab Over a year ago

It needs to work with any number of inputs. And I was expecting things like special classes or functions or libraries.

Melab Over a year ago

Also, N is sixteen bits, but the variable bit is only four, so somehow that doesn't seem like it matches up properly.

Boojum Over a year ago

@Melab - No need for classes or libraries here. But you're right; I was missing a left shift. I also generalized it to any number of bits.

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