> For instance your Eq instance could have been written<br><span style="font-family:courier new,monospace">> x == y = (==) `on` (fst . getTuple)</span><br><br>Sorry, wrong arity:<br>(==) = (==) `on` (fst . getTuple)<br>
<br>Okay for the imperative code.<br><br><div class="gmail_quote">2012/2/5 Yves Parès <span dir="ltr"><<a href="mailto:yves.pares@gmail.com">yves.pares@gmail.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Concerning your first solution, I don't understand why you redefine Eq but not Ord instance. Ord will still work by comparing the tuples and not the first elements of said tuples.<br>Plus the good news is you don't have to do this: just use regular tuples and use sort<b>By </b>or group<b>By </b>functions from Data.List with the 'on' function from Data.Function.<br>
For instance your Eq instance could have been written<br><span style="font-family:courier new,monospace">x == y = (==) `on` (fst . getTuple)</span><br><br>With regular tuples you can write "<span style="font-family:courier new,monospace">sortBy (compare `on` fst)</span>".<br>
<br><br>Plus can you rewrite your original imperative algorithm with the right variable names? You're using a 'd' array that's not been defined.<br><br><br><div class="gmail_quote">2012/2/5 Haisheng Wu <span dir="ltr"><<a href="mailto:freizl@gmail.com" target="_blank">freizl@gmail.com</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5"><font face="'courier new', monospace"><span style="line-height:21px;color:rgb(17,17,17);font-size:13px">a = [1,1,1,1] </span><br style="line-height:21px;color:rgb(17,17,17);font-size:13px">
<span style="line-height:21px;color:rgb(17,17,17);font-size:13px">b = [0,1,2,3] </span><br style="line-height:21px;color:rgb(17,17,17);font-size:13px"><span style="line-height:21px;color:rgb(17,17,17);font-size:13px">d = [0,0,0,0] </span><br style="line-height:21px;color:rgb(17,17,17);font-size:13px">
<br style="line-height:21px;color:rgb(17,17,17);font-size:13px"><span style="line-height:21px;color:rgb(17,17,17);font-size:13px">for i in b: </span><br style="line-height:21px;color:rgb(17,17,17);font-size:13px">
<span style="line-height:21px;color:rgb(17,17,17);font-size:13px"> for j in c: </span><br style="line-height:21px;color:rgb(17,17,17);font-size:13px"><span style="line-height:21px;color:rgb(17,17,17);font-size:13px"> if (i+j)<3: </span><br style="line-height:21px;color:rgb(17,17,17);font-size:13px">
<span style="line-height:21px;color:rgb(17,17,17);font-size:13px"> d[i+j] += a[i] </span> </font><div><br>
</div><div>My just work implementation in Haskell</div><div><a href="http://hpaste.org/57452" target="_blank">http://hpaste.org/57452</a></div><div><br></div><div>Another people implementation in Haskell with Monad and it turns out complex and very imperatively.</div>
<div><a href="http://hpaste.org/57358" target="_blank">http://hpaste.org/57358</a></div><div><br></div><div>Do you have any cool solution in FP way?</div><div><br></div><div>Thanks.</div><div>-Simon</div>
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