Re: [Haskell-cafe] What are side effects in Haskell?

Hi Cristiano, Similarly, any value can be thought of as a list (perhaps singleton), a Maybe (Just), a pair ((,) undefined or (,) mempty), an IO (return), ... (any Applicative). And yet I've heard "everything is a function" on several occasions, but not these others. Hence my (continuing) puzzlement about the source of that idea. I have some speculations: * In pure "OO" programming, everything is an object, so in pure "functional" programming, one might assume everything is a function. I find the term "value-oriented programming" a more accurate label than "functional programming". * C has definitions for functions but assignments for other types. Since pure functional languages eliminate assignment, one might assume that only functions remain. (I also hear people refer to top-level definitions in a Haskell module as "functions", whether they're of function type or not.) Are there other thoughts & insights about the source of the idea that "everything is a function"? Thanks, - Conal On Fri, Jan 2, 2009 at 2:52 AM, Cristiano Paris wrote:

On Tue, Dec 30, 2008 at 8:35 AM, Conal Elliott wrote:

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Everything in Haskell is a function [...]

Where did this idea come from?

I'd say every expression in Haskell denotes a pure value, only some of which are functions (have type a->b for some types a & b).

Maybe more formally correct, but my statement still holds true as any values can be tought as constant functions, even those representing functions themselves.

Cristiano