100 lines
2.6 KiB
Python
100 lines
2.6 KiB
Python
'''Determine if a string has all the same characters'''
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from itertools import groupby
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# firstDifferingCharLR :: String -> Either String Dict
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def firstDifferingCharLR(s):
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'''Either a message reporting that no character changes were
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seen, or a dictionary with details of the first character
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(if any) that differs from that at the head of the string.
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'''
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def details(xs):
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c = xs[1][0]
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return {
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'char': repr(c),
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'hex': hex(ord(c)),
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'index': s.index(c),
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'total': len(s)
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}
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xs = list(groupby(s))
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return Right(details(xs)) if 1 < len(xs) else (
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Left('Total length ' + str(len(s)) + ' - No character changes.')
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)
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# TEST ----------------------------------------------------
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# main :: IO ()
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def main():
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'''Test of 7 strings'''
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print(fTable('First, if any, points of difference:\n')(repr)(
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either(identity)(
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lambda dct: dct['char'] + ' (' + dct['hex'] +
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') at character ' + str(1 + dct['index']) +
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' of ' + str(dct['total']) + '.'
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)
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)(firstDifferingCharLR)([
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'',
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' ',
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'2',
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'333',
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'.55',
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'tttTTT',
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'4444 444'
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]))
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# GENERIC -------------------------------------------------
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# either :: (a -> c) -> (b -> c) -> Either a b -> c
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def either(fl):
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'''The application of fl to e if e is a Left value,
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or the application of fr to e if e is a Right value.
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'''
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return lambda fr: lambda e: fl(e['Left']) if (
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None is e['Right']
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) else fr(e['Right'])
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# identity :: a -> a
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def identity(x):
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'''The identity function.'''
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return x
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# fTable :: String -> (a -> String) ->
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# (b -> String) -> (a -> b) -> [a] -> String
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def fTable(s):
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'''Heading -> x display function -> fx display function ->
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f -> xs -> tabular string.
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'''
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def go(xShow, fxShow, f, xs):
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ys = [xShow(x) for x in xs]
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w = max(map(len, ys))
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return s + '\n' + '\n'.join(map(
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lambda x, y: y.rjust(w, ' ') + ' -> ' + fxShow(f(x)),
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xs, ys
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))
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return lambda xShow: lambda fxShow: lambda f: lambda xs: go(
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xShow, fxShow, f, xs
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)
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# Left :: a -> Either a b
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def Left(x):
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'''Constructor for an empty Either (option type) value
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with an associated string.
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'''
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return {'type': 'Either', 'Right': None, 'Left': x}
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# Right :: b -> Either a b
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def Right(x):
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'''Constructor for a populated Either (option type) value'''
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return {'type': 'Either', 'Left': None, 'Right': x}
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# MAIN ---
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if __name__ == '__main__':
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main()
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