On Fri, Sep 21, 2012 at 8:25 AM, Christopher Howard <span dir="ltr"><<a href="mailto:christopher.howard@frigidcode.com" target="_blank">christopher.howard@frigidcode.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
But this seems rather clunky, especially if I want to attach the values in the new list to variable names afterwards.
</blockquote><div><br></div><div>Agreed. Haskell is not Lisp, so there's no attachment (TH notwithstanding) to variable names ['a'..'z'] if that's what you're thinking. </div><div><br></div><div>
Could you provide the concrete scenario of what you're trying to achieve?</div><div><br></div><br><div>-- Kim-Ee<br>
<br><br><div class="gmail_quote">On Fri, Sep 21, 2012 at 8:25 AM, Christopher Howard <span dir="ltr"><<a href="mailto:christopher.howard@frigidcode.com" target="_blank">christopher.howard@frigidcode.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I have a code situation similar to this simplified one: Let's say that<br>
I've got a value v that is a Maybe type, and values x, y, and z that are<br>
not. x, y, and z are dependent on the value inside v. So I must provide<br>
default values for x, y, and z. An additional complication is that every<br>
calculation returns a new (possibly different) value for v. So, I could<br>
do something like this:<br>
<br>
code:<br>
--------<br>
let (v', x) = case v of<br>
Nothing -> (Nothing, defaultValueOfX)<br>
Just vValue -> f vValue in<br>
let (v'', y) = case v' of<br>
Nothing -> (Nothing, defaultValueOfY)<br>
Just vValue -> g vValue in<br>
let (v''', z) = case v'' of<br>
Nothing -> (Nothing, defaultValueOfZ)<br>
Just vValue -> h vValue in<br>
--------<br>
<br>
(f, g, h represent the calculations I am performing.) In the end, I need<br>
the values of x, y, and z, and the last v value.<br>
<br>
Obviously, the above solution is not very elegant, especially if I add a<br>
few more variables. My other thought was some kind of fold operation,<br>
where I store the functions (calculations) and the default values in a<br>
list, and then fold over the list, applying subsequent values of v or<br>
returning default values, as appropriate. But this seems rather clunky,<br>
especially if I want to attach the values in the new list to variable<br>
names afterwards.<br>
<br>
Is there a better approach?<br>
<span class="HOEnZb"><font color="#888888"><br>
--<br>
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<br></blockquote></div><br></div>