[Haskell-cafe] const is question

[Sebastiaan Visser]

On Jun 14, 2008, at 6:14 PM, odtaa48 wrote:
> hello
> could someone explain the following differing results const id 0    
> 5 -> 5 -- ie. 'takes' the 'last' one
> const (id 0) 5 -> 0 -- ie. 'takes' the 'first' one
>
> Thanks

You can easily see what is happening by rewriting the equations step  
by step. Remember that the const function is (\x y -> x) and the id  
function is (\x -> x).

Example 1:

    const id 0 5
== (const id 0) 5
== id 5
== 5

Example 2:

    const (id 0) 5
== const 0 5
== 0

So, in both cases const takes the first.

--
Sebastiaan.