Sierpinski triangle: Difference between revisions
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and fold/reduce, wrapped as concatMap, can provide the list comprehensions too: |
and fold/reduce, wrapped as concatMap, can provide the list comprehensions too: |
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<lang python> |
<lang python>from functools import (reduce) |
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from functools import reduce |
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# sierpinski :: Int -> String |
# sierpinski :: Int -> String |
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def sierpinski(n): |
def sierpinski(n): |
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'''N rows of a Sierpinksi triangle.''' |
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def go(xs, i): |
def go(xs, i): |
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s = ' ' * (2 ** i) |
s = ' ' * (2 ** i) |
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# concatMap :: (a -> [b]) -> [a] -> [b] |
# concatMap :: (a -> [b]) -> [a] -> [b] |
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def concatMap(f): |
def concatMap(f): |
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'''A concatenated list or string over which a function f |
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has been mapped. |
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The list monad can be derived by using an (a -> [b]) |
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function which wraps its output in a list (using an |
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empty list to represent computational failure). |
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''' |
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return lambda xs: ( |
return lambda xs: ( |
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reduce(add, map(f, xs), []) |
reduce(add, map(f, xs), []) |
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