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<div>Reading around this more i think the extreme case (of what im interested in) is type arithemetic, ie the set of type "inside" the container is not necessarily finite in general, but yes, i see how you construct works.</div>
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<div>So in think for my specific purposes the associated type route is the first place for me to investigate</div>
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Excuse the spelling, sent from a phone with itty bitty keys, it like trying to sow a button on a shirt with a sausage.
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On 7 Jan 2015, at 20:58, Akash Ganesan <<a href="mailto:akaberto@gmail.com">akaberto@gmail.com</a>> wrote:<br>
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<div dir="ltr">If I understand the issue at hand, you want the container, which is<br>
basically a collection of types to be closed under our<br>
operation. Since we are dealing with set of different typed objects,<br>
which is to be closed under a given operation, why not create a new type<br>
that captures the essence of the set (ie., a new data type)? Something<br>
like the following.<br>
<br>
data S = SInt Int<br>
| SChar Char<br>
| STuple (Char, Char) deriving (Show, Eq)<br>
<br>
class MyFoo a where<br>
op :: a -> a<br>
<br>
And the instance goes something like this.<br>
<br>
instance MyFoo S where<br>
op (SInt x) = SInt $ toEnum x<br>
op (SChar x) = STuple (x,x)<br>
op (STuple (x,y)) = SInt $ fromEnum x<br>
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On Tuesday, 6 January 2015 23:13:59 UTC+5:30, Nicholls, Mark wrote:
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">This is reposted from the beginnners….I’ve not done Haskell for a while and was struggling to get anything to work, I’ve hopefully refound my feet.</span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal">Its quite common in maths to have operations in a theory that are (set) closed, i just want to translate that notion to a typeclass</p>
<p class="MsoNormal" style="margin-left:36.0pt"> </p>
<p class="MsoNormal">I have a suggestion that does work</p>
<p class="MsoNormal" style="margin-left:36.0pt"> </p>
<p class="MsoNormal">class Foo m where</p>
<p class="MsoNormal" style="text-indent:36.0pt">op :: m a -> m (S a)</p>
<p class="MsoNormal" style="margin-left:36.0pt"> </p>
<p class="MsoNormal">That is closed, but now were working on types of kind • -> •</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">(S can be a type family or a data type…lets say it’s a type family….probably an associated type (if I know what that means))</p>
<p class="MsoNormal" style="margin-left:36.0pt"> </p>
<p class="MsoNormal">Is this the idiom/pattern i should follow? Or can the closure contraint be expressed directly in a typeclass any other way?</p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> </span></p>
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<p class="MsoNormal" style="margin-left:36.0pt"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"" lang="EN-US">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"" lang="EN-US"> Haskell-Cafe [mailto:<a href="javascript:" target="_blank" gdf-obfuscated-mailto="F2JD1qPceWgJ" onmousedown="this.href='javascript:';return true;" onclick="this.href='javascript:';return true;">haskell-ca...@<wbr>haskell.org</a>]
<b>On Behalf Of </b>Brandon Allbery<br>
<b>Sent:</b> 06 January 2015 1:59 PM<br>
<b>To:</b> Rob Leslie<br>
<b>Cc:</b> Haskell Cafe<br>
<b>Subject:</b> Re: [Haskell-cafe] Haskeline and asynchronous messages</span></p>
<p class="MsoNormal" style="margin-left:36.0pt"> </p>
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<p class="MsoNormal" style="margin-left:36.0pt">On Tue, Jan 6, 2015 at 3:27 AM, Rob Leslie <<a href="javascript:" target="_blank" gdf-obfuscated-mailto="F2JD1qPceWgJ" onmousedown="this.href='javascript:';return true;" onclick="this.href='javascript:';return true;">r...@mars.org</a>>
wrote:</p>
<p class="MsoNormal" style="margin-left:36.0pt">Does anyone have a suggestion on using Haskeline in an environment where another thread may be writing messages to the terminal -- is it possible to somehow print incoming messages above the input line without
disturbing the input line?</p>
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<p class="MsoNormal" style="margin-left:36.0pt"> </p>
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<p class="MsoNormal" style="margin-left:36.0pt">Terminals don't really work that way; you need to be looking at something like curses or vty. </p>
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<p class="MsoNormal" style="margin-left:36.0pt"> </p>
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<p class="MsoNormal" style="margin-left:36.0pt">-- </p>
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<p class="MsoNormal" style="margin-left:36.0pt">brandon s allbery kf8nh sine nomine associates</p>
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<p class="MsoNormal" style="margin-left:36.0pt"><a href="javascript:" target="_blank" gdf-obfuscated-mailto="F2JD1qPceWgJ" onmousedown="this.href='javascript:';return true;" onclick="this.href='javascript:';return true;">allb...@gmail.com</a>
<a href="javascript:" target="_blank" gdf-obfuscated-mailto="F2JD1qPceWgJ" onmousedown="this.href='javascript:';return true;" onclick="this.href='javascript:';return true;">ball...@sinenomine.net</a></p>
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<p class="MsoNormal" style="margin-left:36.0pt">unix, openafs, kerberos, infrastructure, xmonad <a href="http://sinenomine.net" target="_blank" onmousedown="this.href='http://www.google.com/url?q\75http%3A%2F%2Fsinenomine.net\46sa\75D\46sntz\0751\46usg\75AFQjCNHBnww-LlA19Cq0MQZiTCtVEC-wow';return true;" onclick="this.href='http://www.google.com/url?q\75http%3A%2F%2Fsinenomine.net\46sa\75D\46sntz\0751\46usg\75AFQjCNHBnww-LlA19Cq0MQZiTCtVEC-wow';return true;">http://sinenomine.net</a></p>
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