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