[Haskell-cafe] general

[Jed Brown]

On  8 Dec 2007, ryanbloor at hotmail.com wrote:

> Function A is a function that passes its input into B
> Function B is a function that does something once. 
>
> How do I make it so function A is done multiple times without adding a
> third function?

By this, do you mean that you have functions f, g

f :: a -> a
g :: a -> b

and you want

b . f . f . f . ... . f

where there are n applications of f?  If so, then

g . (!! n) . iterate f

will do the trick.  Alternatively, you can produce the infinite list, as
in:

map (^2) . iterate succ $ 0      -- [0,1,4,9,16,25,36,49,64,81 ...

Jed
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