3 ms·

what do you mean by that? all functions in haskell are pure unless you explicitly use unsafePreformIO or similar (which is rare to ever have to do)

agnishom 2y ago
It doesn't have great support for Dependent Types
- Tainnor 2y ago
  what does that have to do with purity?
  - agnishom 2y ago
    Nothing, but arguably a language with dependent types is more Haskell than Haskell
eru 2y ago
They can still have side-effects like non-termination. But I didn't mean purity in that formal sense. I meant that Haskell is plenty pragmatic in its design.
- kreetx 2y ago
  To me, "pure" means referential transparency: same input, same output. So an `Int -> Int` function will return same result on same argument. So, similar to `Int -> IO Int`, the function (action) will return an Int after interacting with outside world, `IO` tracking the fact that this is the case.
- tromp 2y ago
  Lambda calculus is as pure as can be, and also has terms that don't normalize. That is not considered a side effect. A better example of impurity in Haskell for pragmatic's sake is the trace function, that can be used to print debugging information from pure functions.
  - eru 2y ago
    > Lambda calculus is as pure as can be, and also has terms that don't normalize. That is not considered a side effect. Many typed lambda calculi do normalise. You can also have a look https://dhall-lang.org/ https://dhall-lang.org/ for some pragmatic that normalises. > A better example of impurity in Haskell for pragmatic's sake is the trace function, that can be used to print debugging information from pure functions. Well, but that's just unsafePerformIO (or unsafePerformIO-like) stuff under the hood; that was already mentioned.
- instig007 2y ago
  > They can still have side-effects like non-termination. you can still have total functions that don't finish in humanly/business reasonable amount of time.
  - eru 2y ago
    Yes? Just like pure functions can use more memory than your system has. Or computing them can cause your CPU to heat up, which is surely a side-effect.

agnishom 2y ago

It doesn't have great support for Dependent Types

Tainnor 2y ago
what does that have to do with purity?
- agnishom 2y ago
  Nothing, but arguably a language with dependent types is more Haskell than Haskell

eru 2y ago

They can still have side-effects like non-termination. But I didn't mean purity in that formal sense. I meant that Haskell is plenty pragmatic in its design.

kreetx 2y ago
To me, "pure" means referential transparency: same input, same output. So an `Int -> Int` function will return same result on same argument. So, similar to `Int -> IO Int`, the function (action) will return an Int after interacting with outside world, `IO` tracking the fact that this is the case.
tromp 2y ago
Lambda calculus is as pure as can be, and also has terms that don't normalize. That is not considered a side effect. A better example of impurity in Haskell for pragmatic's sake is the trace function, that can be used to print debugging information from pure functions.
- eru 2y ago
  > Lambda calculus is as pure as can be, and also has terms that don't normalize. That is not considered a side effect. Many typed lambda calculi do normalise. You can also have a look https://dhall-lang.org/ https://dhall-lang.org/ for some pragmatic that normalises. > A better example of impurity in Haskell for pragmatic's sake is the trace function, that can be used to print debugging information from pure functions. Well, but that's just unsafePerformIO (or unsafePerformIO-like) stuff under the hood; that was already mentioned.
instig007 2y ago
> They can still have side-effects like non-termination. you can still have total functions that don't finish in humanly/business reasonable amount of time.
- eru 2y ago
  Yes? Just like pure functions can use more memory than your system has. Or computing them can cause your CPU to heat up, which is surely a side-effect.