MonadPlus is `or` semantics, as is Alternative. It does, indeed, reflect the Applicative/Monad difference.<br><br><div class="gmail_quote">On Sat, Oct 29, 2011 at 8:02 PM, Gregory Crosswhite <span dir="ltr"><<a href="mailto:gcrosswhite@gmail.com">gcrosswhite@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div style="word-wrap:break-word">Hey everyone,<div><br></div><div>What is the difference between MonadPlus and Alternative? In my mind, it would make sense for the difference to be that the former provides "and" semantics (i.e., x `mplus` y means do both x and y) whereas the latter provides "or" semantics (i.e., x <|> y means do x or y but not both). However, when I look at the instances defined for List I see that it is exactly the same as MonadPlus.</div>
<div><br></div><div>So is there any difference between the interpretation of MonadPlus and Alternative, or is the only difference between them that the former applies to Monad whereas the latter applies to Applicative?</div>
<div><br></div><div>Also, along similar lines, why does MonadPlus exist when it is essentially just a special case of Monoid? (That is, any MonadPlus instance could be equivalently cast as a Monoid instance.)</div><div><br>
</div><div>Thanks!</div><div>Greg</div></div><br>_______________________________________________<br>
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