The key here is to use the wildcard _ in your pattern matching, which will
match any value.
You can also bundle your arguments in a tuple, without needing to use
records.
forecastProtected : Maybe Float -> Maybe Float -> Maybe Float -> (List Int)
-> List Float
forecastProtected q d b months =
case (q, d, b) of
( Just qF, Just dF, Just bF ) -> forecast qF dF bF months
_ -> []
Note also that your syntax was wrong in your case: Maybe is a type, not a
value, so you can never use it in a pattern match. You need to match either
against the constructors (Just, Nothing) or wildcards, or variables.
On Wed, Aug 3, 2016 at 4:44 PM, Austin B <[email protected]> wrote:
> I am trying to ensure that three arguments to a function are all not
> Nothing.
>
> Right now I have this (below), which works, but uses "withDefault." I want
> to avoid this because the default values are meaningless and I want to
> clearly and fundamentally avoid any possible situation where a Nothing gets
> through to the "else" part
>
> forecastProtected : Maybe Float -> Maybe Float -> Maybe Float -> (List
> Int) -> List Float
> forecastProtected q d b months =
> if List.any (\m -> m == Nothing) [q, e, b] then []
> else
> forecast
> (withDefault 0 q)
> (withDefault 0 d)
> (withDefault 0 b)
> months
>
>
> I am hoping to do something like this:
> forecastProtected : Maybe Float -> Maybe Float -> Maybe Float -> (List
> Int) -> List Float
> forecastProtected q d b months =
> let
> params = {q = q, d = d, b = b}
> in
> case params of
> { Just qF, Just dF, Just bF } -> forecast qF dF bF months
> { Maybe, Maybe, Maybe } -> []
>
> which more clearly shows what I am trying to achieve. Could someone point
> me to the appropriate syntax for this? Also the 'F' in qF, dF, and bF are
> "Float" to avoid masking of variables (not sure how this happens in elm);
> it would be best if I could avoid this complication too.
>
> Thanks everyone for all your help as I'm getting started!
> Austin
>
>
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