Binary digits: Difference between revisions
→Python :: Custom functions: Added a more specialised decomposition of an integer to a list of booleans
(→{{header|Python}}: Added a variant using a more general showIntAtBase function) |
(→Python :: Custom functions: Added a more specialised decomposition of an integer to a list of booleans) |
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Line 3,024:
if __name__ == '__main__':
main()</lang>
Or, using a more specialised function to decompose an integer to a list of boolean values:
<lang python>'''Decomposition of an integer to a string of booleans.'''
# boolsFromInt :: Int -> [Bool]
def boolsFromInt(n):
'''List of booleans derived by binary
decomposition of an integer.'''
def go(x):
return Just((x // 2, bool(x % 2))) if x else Nothing()
return unfoldl(go)(n)
# stringFromBools :: [Bool] -> String
def stringFromBools(xs):
'''Binary string representation of a
list of boolean values.'''
def oneOrZero(x):
return '1' if x else '0'
return ''.join(map(oneOrZero, xs))
# TEST ----------------------------------------------------
# main :: IO()
def main():
'''Test'''
print(unlines(map(
compose(stringFromBools)(boolsFromInt),
enumFromTo(0)(16)
)))
# GENERIC -------------------------------------------------
# Just :: a -> Maybe a
def Just(x):
'''Constructor for an inhabited Maybe (option type) value.'''
return {'type': 'Maybe', 'Nothing': False, 'Just': x}
# Nothing :: Maybe a
def Nothing():
'''Constructor for an empty Maybe (option type) value.'''
return {'type': 'Maybe', 'Nothing': True}
# compose (<<<) :: (b -> c) -> (a -> b) -> a -> c
def compose(g):
'''Right to left function composition.'''
return lambda f: lambda x: g(f(x))
# enumFromTo :: (Int, Int) -> [Int]
def enumFromTo(m):
'''Integer enumeration from m to n.'''
return lambda n: list(range(m, 1 + n))
# unfoldl(lambda x: Just(((x - 1), x)) if 0 != x else Nothing())(10)
# -> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
# unfoldl :: (b -> Maybe (b, a)) -> b -> [a]
def unfoldl(f):
'''Dual to reduce or foldl.
Where these reduce a list to a summary value, unfoldl
builds a list from a seed value.
Where f returns Just(a, b), a is appended to the list,
and the residual b is used as the argument for the next
application of f.
When f returns Nothing, the completed list is returned.'''
def go(v):
xr = v, v
xs = []
while True:
mb = f(xr[0])
if mb.get('Nothing'):
return xs
else:
xr = mb.get('Just')
xs.insert(0, xr[1])
return xs
return lambda x: go(x)
# unlines :: [String] -> String
def unlines(xs):
'''A single string derived by the intercalation
of a list of strings with the newline character.'''
return '\n'.join(xs)
# MAIN -------------------------------------------------
if __name__ == '__main__':
main()</lang>
{{Out}}
(Same for both custom function examples above)
<pre>1
10
11
100
101
110
111
1000
1001
1010
1011
1100
1101
1110
1111
10000</pre>
=={{header|Racket}}==
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