# [Haskell-cafe] Function composition questions from a newbie

newbie2009 atheist.diehard at yahoo.com
Tue Dec 1 03:12:18 EST 2009

```I am a newbie. Consider this code:

square x = x * x
add3 x y z = x + y + z

leledumbo wrote:
>
>
>
> It doesn't work since add3, when curried (arguments of square "blended"
> with add3's) with 1 argument becomes:
>
> add3 :: Num a => a -> a -> a
>
> which is a function that accepts 2 arguments and it's not compatible with
> square's a.
>

Thank you so much for your clarification. To understand better, I tried some
definitions
1) composition = (square . add3) 5 -- illegal as you had explained
2) composition x = (square . add3) 1 2 3 -- legal, but why? what is the
significance of x
3) composition x = (square . add3) x -- legal, but why?
4) composition x y = (square . add3) x y -- legal, but why?
5) composition x = (square . add3) x 3 -- legal, but why?

I dont understand why the above functions are legal, and what arguments they
need. Could you please give an example of how to invoke it?

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