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elm

Elm specify number to me Int

I am trying to see if length of a given list equals some number. However == expects two numbers not Int, so even when I type (==) 1 type is still number -> Bool so finally when I pipe in result of lenght I get compilation error:

-- TYPE MISMATCH ---------------------------------------------------------- REPL

This function cannot handle the argument sent through the (|>) pipe:

4|   List.length |> ((==) 1)
                     ^^^^^^

The argument is:

List a -> Int

But (|>) is piping it to a function that expects:

number

Hint: Only Int and Float values work as numbers.

So how can I specify that my constant is an Int as opposed to number variable?

Solution

  • Use >> to compose functions.

    isLengthOne = List.length >> ((==) 1) is a function that checks that the length of a list is 1.

    |> pipes the output of one statement to the input of the next.

    So aList |> List.length |> ((==) 1) would check aList.