Re: [elm-discuss] Re: Pattern matching using existing bound variables

[Max Goldstein]

That's exactly Maybe.withDefault "something", which is a great example of 
partial application. 

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Re: [elm-discuss] Re: Pattern matching using existing bound variables

[Duane Johnson]

Ah, that makes sense. Take the value out of the Maybe box.

On Dec 5, 2016 2:32 PM, "David Andrews"  wrote:

> That is what I meant.  I will often use this pattern as follows:
>
> orSomething : Maybe String -> String
> orSomething str =
>   case str of
> Just str -> str
> Nothing -> "something"
>
> I realize, though, that I misunderstood the original question.
>
> On Monday, December 5, 2016 at 3:25:07 PM UTC-5, Duane Johnson wrote:
>>
>>
>> On Sun, Dec 4, 2016 at 6:53 PM, David Andrews  wrote:
>>
>>> I expect that you are actually looking to do something like this:
>>>   let
>>> x = 1
>>>   in
>>> case something of
>>>   Just x -> ...
>>>   Nothing -> ...
>>>
>>
>> David, are you sure you didn't mean the following?
>>
>> case something of
>>
>>Just 1 -> ...
>>
>>Nothing -> ...
>>
>>
>> It seems strange to include a shadowed variable `x` as in your expected
>> code.
>>
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Re: [elm-discuss] Re: Pattern matching using existing bound variables

[David Andrews]

That is what I meant.  I will often use this pattern as follows:

orSomething : Maybe String -> String
orSomething str =
  case str of
Just str -> str
Nothing -> "something"

I realize, though, that I misunderstood the original question.  

On Monday, December 5, 2016 at 3:25:07 PM UTC-5, Duane Johnson wrote:
>
>
> On Sun, Dec 4, 2016 at 6:53 PM, David Andrews  > wrote:
>
>> I expect that you are actually looking to do something like this:
>>   let
>> x = 1
>>   in
>> case something of
>>   Just x -> ...
>>   Nothing -> ...
>>
>
> David, are you sure you didn't mean the following?
>
> case something of
>
>Just 1 -> ... 
>
>Nothing -> ...
>
>
> It seems strange to include a shadowed variable `x` as in your expected 
> code.
>

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Re: [elm-discuss] Re: Pattern matching using existing bound variables

[Duane Johnson]

On Sun, Dec 4, 2016 at 6:53 PM, David Andrews  wrote:

> I expect that you are actually looking to do something like this:
>   let
> x = 1
>   in
> case something of
>   Just x -> ...
>   Nothing -> ...
>

David, are you sure you didn't mean the following?

case something of

   Just 1 -> ...

   Nothing -> ...


It seems strange to include a shadowed variable `x` as in your expected
code.

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[elm-discuss] Re: Pattern matching using existing bound variables

[David Andrews]

I think the problem is slightly different than you think.  The reason the 
compiler complains about the redundant pattern is that "x" already matches 
everything.  There are no more cases for "_" to handle.

This compiles with no problem:
  let
x = 1
  in
case something of
  x -> ...


I expect that you are actually looking to do something like this:
  let
x = 1
  in
case something of
  Just x -> ...
  Nothing -> ...

On Sunday, December 4, 2016 at 6:05:10 AM UTC-5, Michał Podwórny wrote:
>
> Thanks for clearing things out!
>
> W dniu niedziela, 4 grudnia 2016 02:40:41 UTC+1 użytkownik Michał Podwórny 
> napisał:
>>
>> Hi,
>>
>> Consider this:
>> let
>>   x = 1
>> in
>>   case something of
>> x -> (...)
>> _ -> (...)
>>
>> The compiler will complain that "The following pattern is redundant", 
>> pointing to the wildcard. I assume that Elm ignores the fact that "x" is 
>> already bound, re-binds it in the first case match and that indeed makes 
>> the wildcard redundant. I know how I would do this in Elixir: I'd put "^" 
>> before "x" to explicitly say not to re-bind the x variable. Is there 
>> something like this in Elm?
>>
>

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[elm-discuss] Re: Pattern matching using existing bound variables

[Michał Podwórny]

Thanks for clearing things out!

W dniu niedziela, 4 grudnia 2016 02:40:41 UTC+1 użytkownik Michał Podwórny 
napisał:
>
> Hi,
>
> Consider this:
> let
>   x = 1
> in
>   case something of
> x -> (...)
> _ -> (...)
>
> The compiler will complain that "The following pattern is redundant", 
> pointing to the wildcard. I assume that Elm ignores the fact that "x" is 
> already bound, re-binds it in the first case match and that indeed makes 
> the wildcard redundant. I know how I would do this in Elixir: I'd put "^" 
> before "x" to explicitly say not to re-bind the x variable. Is there 
> something like this in Elm?
>

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