<div>(*>) and (<*) could be used to apply recognizing parsers for the discarded half. This makes a huge gain for uu-parsinglib. uu-parsinglib's P_m monad could be extended just as it has done with P_f and P_h to also wrap its existing R monad, which would let it apply the parser as a recognizer efficiently.</div>
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<div>And for parsimony it allows me to treat that side of the alternative grammar as a right seminearring ignoring the argument, this increases sharing opportunities for my grammar fragments, because pure nodes in recognizers can be treated as epsilons in the grammar and safely elided.</div>
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<div>-Edward Kmett<br></div>
<div class="gmail_quote">On Wed, Aug 19, 2009 at 11:40 AM, Ross Paterson <span dir="ltr"><<a href="mailto:ross@soi.city.ac.uk">ross@soi.city.ac.uk</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<div class="im">On Mon, Jun 29, 2009 at 01:45:45PM +0100, Ross Paterson wrote:<br>> The proposal is that the following functions<br>><br>> (<$) :: Functor f => a -> f b -> f a<br>> (*>) :: Applicative f => f a -> f b -> f b<br>
> (<*) :: Applicative f => f a -> f b -> f a<br>> some :: Alternative f => f a -> f [a]<br>> many :: Alternative f => f a -> f [a]<br>><br>> are moved into the corresponding classes, with the existing implementations<br>
> as default definitions.<br><br></div>Henning asked for concrete examples (i.e. code) where this would give<br>a substantial performance win while still defining the same function,<br>including termination properties. (But it seems reasonable not to rely<br>
on RULES to improve the asymptotic complexity.)<br><br>I gave an example for (<$). Does anyone have concrete examples for<br>the others?<br>
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