Mutability in functional programming

Question

First I am a Haskell newbie. I\'ve read this: Immutable functional objects in highly mutable domain And my question is nearly the same -- how to efficiently write algorithms whe

Answer 1

In ML derivatives (such as OCaml, SML, F#), there are "references", which can be used as mutable variables.

In Haskell, this isn't cleanly handled. State is simply not covered by the usual "purely functional" style. Pure FP languages deal with "eternal truths", and are thus not very suitable for working with "ephemeral truths" (although it can be done, definitely).

However, yes, sometimes we need mutable state. A language such as ATS incorporates linear types for handling destructive updates and safe resource manipulation.