Re:Overthinking Fizzbuzz with Monoids
by chicago_wade on Thursday September 14, 2017 @03:42PM
(#15251824)
By the way, speaking of sum, I find it a bit strange that Python allows
but not
Intuitively I would have expected the latter to be possible given the former but I guess it comes down to how the + operator and the sum function are implemented in Python, such that counter to my expectation sum is not a function that "applies the + operator" to it's arguments. The notion that this is how it should work stems from my impression that "sum" belongs to the same family as do "map", "reduce" and "apply" -- that these are somehow "functional" in nature in the sense that is observed in the Lisp family of languages.
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I guess sum was only implemented to support numeric values. However you can easily roll your own:
>>> def add(it):
... return reduce(lambda x, y: x + y, it)
...
>>> add(['hello ', 'world'])
'hello world'
>>> add(x for x in xrange(10))
45
>>> import operator
>>> def add(it):
... return reduce(operator.add, it)
Re:Overthinking Fizzbuzz with Monoids
by chicago_wade on Thursday September 14, 2017 @04:02PM
(#15251985)
>>> import operator
>>> def add(it):
... return reduce(operator.add, it)
Looping back to why sum doesn't work with strings, it looks like they implemented it like this:
>>> def sum(it):
... return reduce(operator.add, it, 0)
In a typed language you could use type inference and use the inferred type's zero value (if the language has such a concept for all types like for example Go does). In Python I guess you could fall back to None, but then you'd have code that doesn't behave consistently for all inputs.