[Haskell-cafe] Purely logical programming language

[Jan Christiansen]

Hi,

On 26.05.2009, at 21:24, Lauri Alanko wrote:

> Mercury also has type classes and other Haskellisms, so if you're
> interested in "doing Prolog the Haskell way", you should definitely
> have a look at it.

I have to admit that I am not very familiar with Mercury. But if you  
are looking for "doing Prolog the Haskell way" <advertise>you can also  
have a look at Curry</advertise>. Curry is a lazy functional logic  
programming language that has a Haskell like syntax (http://www.curry-language.org/ 
). Besides standard functional features it provides non-determinism  
and narrowing. In contrast to Haskell overlapping rules in function  
definitions induce non-determinism. For example the following  
"function" non-deterministically inserts an element at each position  
of a list.

  insert :: a -> [a] -> [a]
  insert x xs       = x : xs
  insert x (y:ys) = y : insert x ys

 From the side-effects point of view Curry is very boring as it does  
not provide type classes but there is one monad namely the IO monad  
for doing side effects.

Cheers, Jan