<div>> Alternatively: flip (foldr id)<br><div class="HOEnZb"></div></div><div><br></div><div>Very cool, but... </div><div><br></div><div>Prelude> import qualified Data.Foldable as F</div><div><div>Prelude F> :t F.foldr id</div>
</div><div>F.foldr id :: F.Foldable t => b -> t (b -> b) -> b</div><div><br></div><div><br></div><div>{- Generalizing -}</div><div><br></div><div><div>Prelude F> import qualified Control.Category as C</div>
</div><div>Prelude F C> :t F.foldr (C..) C.id</div><div>F.foldr (C..) C.id :: (F.Foldable t, C.Category cat) => t (cat b b) -> cat b b</div><div><br></div><div><br></div><div>{- Sneaky type-specialization -}</div>
<div><br></div><div><div>Prelude F C> :t F.foldr C.id</div><div>F.foldr C.id :: F.Foldable t => b -> t (b -> b) -> b</div></div><div><br></div><br><div class="gmail_quote">On Sat, Oct 27, 2012 at 3:09 AM, Ross Paterson <span dir="ltr"><<a href="mailto:ross@soi.city.ac.uk" target="_blank">ross@soi.city.ac.uk</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="HOEnZb"><div class="h5">On Fri, Oct 26, 2012 at 07:41:18PM +0100, Greg Fitzgerald wrote:<br>
> I've recently found myself using the expression: "foldr (.) id" to<br>
> compose a list (or Foldable) of functions. It's especially useful<br>
> when I need to map a function over the list before composing. Does<br>
> this function, or the more general "foldr fmap id", defined in a<br>
> library anywhere? I googled and hoogled, but no luck so far.<br>
<br>
</div></div>Alternatively: flip (foldr id)<br>
<div class="HOEnZb"><div class="h5"><br>
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