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Named lambdas are discouraged as un-Pythonic for what it's worth. The other point in the article was that your process has now hard-coded even and sum, and com

by nimish 9y ago

Named lambdas are discouraged as un-Pythonic for what it's worth. The other point in the article was that your process has now hard-coded even and sum, and composing them in python is a bit unwieldy. I've run into a number of cases where it's just easier in python to write out the loops than string comprehensions or map/filter/reduces together because there's no threading macro or haskell's functional apply operator.

whalesalad 9y ago
You can compose it all together in a relatively straightforward manner using functions in the stdlib. I agree that it is nicer with a threading macro, but is this so bad? def even(x): return x % 2 == 0 def inc(x): return x + 1 def process(seq): return sum(map(inc, filter(even, seq)))
- emidln 9y ago
  You can also easily write pipeline() (which is just a reduction over callables inside a lambda[0]) such that: process = pipeline(partial(filter, even), partial(map, inc), sum) process(some-iterable) I'll grant that it's not syntactically ideal (this is the tradeoff the thrush combinator (pipeline) running as a function instead of working as a macro. The benefit of being able to follow down the program as it works remains. (def process [xs] (->> xs (filter even?) (map inc) (reduce +))) (process some-iterable) If you compare a function-based approach[1] (instead of a macro) you might get: (def process (pipeline (partial filter even?) (partial map inc) (partial reduce +))) process(some-iterable) [0] A sample Python definiton (python doesn't have compose to reverse): def pipeline(*fns): return reduce(lambda f, g: lambda *xs, **ys: g(f(*xs, **ys)), fns) [1] A clojure implementation: (defn pipeline [& fs] (apply compose (reverse fs)))
  - lvh 9y ago
    That's true, but a bit of an unfortunate example since the point of the article is to demonstrate transducers, and instead this demonstrates a bunch of chained collection functions.

by nimish 9y ago

whalesalad 9y ago

You can compose it all together in a relatively straightforward manner using functions in the stdlib. I agree that it is nicer with a threading macro, but is this so bad? def even(x): return x % 2 == 0 def inc(x): return x + 1 def process(seq): return sum(map(inc, filter(even, seq)))

emidln 9y ago
You can also easily write pipeline() (which is just a reduction over callables inside a lambda[0]) such that: process = pipeline(partial(filter, even), partial(map, inc), sum) process(some-iterable) I'll grant that it's not syntactically ideal (this is the tradeoff the thrush combinator (pipeline) running as a function instead of working as a macro. The benefit of being able to follow down the program as it works remains. (def process [xs] (->> xs (filter even?) (map inc) (reduce +))) (process some-iterable) If you compare a function-based approach[1] (instead of a macro) you might get: (def process (pipeline (partial filter even?) (partial map inc) (partial reduce +))) process(some-iterable) [0] A sample Python definiton (python doesn't have compose to reverse): def pipeline(*fns): return reduce(lambda f, g: lambda *xs, **ys: g(f(*xs, **ys)), fns) [1] A clojure implementation: (defn pipeline [& fs] (apply compose (reverse fs)))
- lvh 9y ago
  That's true, but a bit of an unfortunate example since the point of the article is to demonstrate transducers, and instead this demonstrates a bunch of chained collection functions.