Re: [Haskell-cafe] pointer equality

On Wed, 20 Jul 2011 12:48:48 -0300 Thiago Negri wrote:

Is it possible to implement (==) that first check these thunks before evaluating it? (Considering both arguments has pure types).

E.g.,

Equivalent thunks, evaluates to True, does not need to evaluate its arguments: [1..] == [1..]

Thunks are just expressions and equality of expressions is undecidable in any Turing-complete language (like any general-purpose programming language). Note that syntactical equality is not sufficient because (==) should be referentially transparent. Pedro