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Nothing overrated about it. Pure functions lack state. Without state, no state bugs. State bugs make up a great share of bugs in this world. Thus your program w

by hkjgkjy 10y ago

Nothing overrated about it. Pure functions lack state. Without state, no state bugs. State bugs make up a great share of bugs in this world. Thus your program written in a functional language lacks those bugs. Also just nice to have a = function, instead of having each class implement a .equals() method (looking at you, java).

jeff_marshall 10y ago
Yes, instead you have parameter passing bugs (what, it's not state if it's not an implicit global variable?). I suspect the bugs have more to do with what is considered an acceptable design pattern (and resulting cognitive load) than the state-passing style.
- nightski 10y ago
  Well not really in a language as strongly typed as Haskell. At least, it provides you the type machinery to prevent a large source of these sort of bugs. It's not the end of the story either, there are even much more powerful languages than it which are still in infancy.
  - jeff_marshall 10y ago
    If you would have substituted coq (or even ACL2 with guards checking enabled...) in the place of haskell I would agree. hindley-milner style type checking is nice, but once you admit that things like arrays exist (rather than just algebraic data types or cons cells), the power of languages like haskell is in design patterns like map() and reduce() rather than the type checker, IMO. Having worked in functional languages with an imperative bent (esp. ACL2 in the context of modeling microprocessors), you can get an awful lot of mileage out of a good static proof strategy that can be instantiated over a known design pattern (equivalence relations, map, reduce, etc) even when you pass a single, huge, state object to all your top level functions.
    - codygman 10y ago
      > hindley-milner style type checking is nice, but once you admit that things like arrays exist How are these related? Haskell has arrays. Arrays can be represented as algebraic data types as well. What is it you think Haskell has trouble representing?
eudox 10y ago
Equality, like copying, is often more complicated than that. You often run into a problem where you need a domain-specific equality function for your objects. Which is not to say that automatic derivation of generic functions is not useful, but it's not really a game changer.

by hkjgkjy 10y ago

jeff_marshall 10y ago

Yes, instead you have parameter passing bugs (what, it's not state if it's not an implicit global variable?). I suspect the bugs have more to do with what is considered an acceptable design pattern (and resulting cognitive load) than the state-passing style.

nightski 10y ago
Well not really in a language as strongly typed as Haskell. At least, it provides you the type machinery to prevent a large source of these sort of bugs. It's not the end of the story either, there are even much more powerful languages than it which are still in infancy.
- jeff_marshall 10y ago
  If you would have substituted coq (or even ACL2 with guards checking enabled...) in the place of haskell I would agree. hindley-milner style type checking is nice, but once you admit that things like arrays exist (rather than just algebraic data types or cons cells), the power of languages like haskell is in design patterns like map() and reduce() rather than the type checker, IMO. Having worked in functional languages with an imperative bent (esp. ACL2 in the context of modeling microprocessors), you can get an awful lot of mileage out of a good static proof strategy that can be instantiated over a known design pattern (equivalence relations, map, reduce, etc) even when you pass a single, huge, state object to all your top level functions.
  - codygman 10y ago
    > hindley-milner style type checking is nice, but once you admit that things like arrays exist How are these related? Haskell has arrays. Arrays can be represented as algebraic data types as well. What is it you think Haskell has trouble representing?

eudox 10y ago

Equality, like copying, is often more complicated than that. You often run into a problem where you need a domain-specific equality function for your objects. Which is not to say that automatic derivation of generic functions is not useful, but it's not really a game changer.