# Iterate

From HaskellWiki

Revision as of 01:34, 20 October 2006 by CaleGibbard (talk | contribs)

This page documents some ways in which the Haskell prelude function iterate can be implemented.

First, the direct recursive way seen in the Haskell report:

```
iterate f x = x : iterate f (f x)
```

We can also write it in terms of scanl or scanl1 and repeat:

```
iterate f x = scanl f x (repeat x)
```

```
iterate f x = scanl1 f (repeat x)
```

Or in terms of fix:

```
iterate f x = fix ((x:) . map f)
```