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A monoid in python
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| from collections import defaultdict | |
| class Monoid(): | |
| def __init__(self, zero, foldOp, liftFunctor=None): | |
| self.store = defaultdict(zero) | |
| self.liftFunctor = liftFunctor | |
| self.foldOp = foldOp | |
| self.zero = zero | |
| def fold(self, key, vals): | |
| ''' reduce is a subset of fold :) ''' | |
| _key = self.liftFunctor(key) | |
| self.store[_key] = reduce(self.foldOp, [reduce(self.foldOp, vals), self.store[_key]]) | |
| def __call__(self, args): | |
| self.fold("default", args) | |
| def __str__(self): | |
| return str(self.store) | |
| if __name__ == '__main__': | |
| sumAggregator = Monoid(lambda : 0, lambda val1, val2: val1+val2, lambda key: key) | |
| sumAggregator([1, 2, 3, 4, 5]) | |
| print sumAggregator |
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