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But comprehensions are also a functional idiom.

bad_user 8y ago
FP means referential transparency. For-comprehensions operate on iterators and iterators are not FP, being a very dirty and mutable protocol. Do not confuse FP with declarative programming or with laziness. FP often implies declarative APIs and laziness but not vice-versa.
- duckerude 8y ago
  Python's comprehensions were lifted from Haskell, and its map and filter functions also operate on iterables. They can't be purely functional because of the surrounding language, but they do follow a functional style. (expr for item in iterable if cond) is more or less another way to spell map(lambda item: expr, filter(lambda item: cond, iterable)), except readable. You could define "functional programming" to absolutely require referential transparency, but that's not what the rest of the thread is doing.
  - kthielen 8y ago
    I don't mean to be pedantic but IIRC Python's comprehensions actually came from the SETL language. Obviously it's ultimately the same thing either way, but that's the lineage (SETL -> ABC -> Python). https://en.wikipedia.org/wiki/SETL https://en.wikipedia.org/wiki/SETL
    - duckerude 8y ago
      I didn't know about SETL, that's interesting. https://docs.python.org/3/howto/functional.html#generator-expressions-and-list-comprehensions https://docs.python.org/3/howto/functional.html#generator-ex... claims Python borrowed them from Haskell, but the ABC link seems more likely.
      - zephyrfalcon 8y ago
        ABC didn't have list comprehensions though, in spite of being influenced by SETL. As I recall, Python did get them from Haskell, which in turn got them from Miranda, which got them from KRC. Before that it gets fuzzy, but it's likely that SETL was eventually at the root of it.
- deleted 8y ago
  [deleted]
bunderbunder 8y ago
Yeah, sorry, I didn't mean to say that Python's not functional without a "map" function. More trying to guess where that perception comes from. Python's comprehensions are (I believe) inspired by Haskell, but, if you're not a Haskeller, you're probably more used to other ways of doing things.
lmm 8y ago
The version Python has is awkward to work with, to the point that many Haskell programmers don't even realise it exists. The "do notation" style is much clearer than the "comprehension" style; unfortunately Python has no equivalent.

FP means referential transparency. For-comprehensions operate on iterators and iterators are not FP, being a very dirty and mutable protocol. Do not confuse FP with declarative programming or with laziness. FP often implies declarative APIs and laziness but not vice-versa.

duckerude 8y ago
Python's comprehensions were lifted from Haskell, and its map and filter functions also operate on iterables. They can't be purely functional because of the surrounding language, but they do follow a functional style. (expr for item in iterable if cond) is more or less another way to spell map(lambda item: expr, filter(lambda item: cond, iterable)), except readable. You could define "functional programming" to absolutely require referential transparency, but that's not what the rest of the thread is doing.
- kthielen 8y ago
  I don't mean to be pedantic but IIRC Python's comprehensions actually came from the SETL language. Obviously it's ultimately the same thing either way, but that's the lineage (SETL -> ABC -> Python). https://en.wikipedia.org/wiki/SETL https://en.wikipedia.org/wiki/SETL
  - duckerude 8y ago
    I didn't know about SETL, that's interesting. https://docs.python.org/3/howto/functional.html#generator-expressions-and-list-comprehensions https://docs.python.org/3/howto/functional.html#generator-ex... claims Python borrowed them from Haskell, but the ABC link seems more likely.
    - zephyrfalcon 8y ago
      ABC didn't have list comprehensions though, in spite of being influenced by SETL. As I recall, Python did get them from Haskell, which in turn got them from Miranda, which got them from KRC. Before that it gets fuzzy, but it's likely that SETL was eventually at the root of it.
deleted 8y ago
[deleted]

bunderbunder 8y ago

Yeah, sorry, I didn't mean to say that Python's not functional without a "map" function. More trying to guess where that perception comes from. Python's comprehensions are (I believe) inspired by Haskell, but, if you're not a Haskeller, you're probably more used to other ways of doing things.

lmm 8y ago

The version Python has is awkward to work with, to the point that many Haskell programmers don't even realise it exists. The "do notation" style is much clearer than the "comprehension" style; unfortunately Python has no equivalent.