How to define a function that takes no input

[Pabich Pawel]

Hi,

I started playing with Elm a couple of days ago and I can't stop :).

I'm trying to define a function that always returns the same data and takes no input parameters. How would I define it in Elm ?

Thanks

Pawel

[Pabich Pawel]

It looks like I found it:

init: a -> Model

init = always 0

[Bobby Eickhoff]

I'm curious -- since the function takes no input parameters and always returns the same data, why use a function?  That sounds like a constant.

[Pabich Pawel]

Hi Bobby,

I wanted to use this to implement the init method (same approach that is used in elm architecture). Just in my case I don't any input. I'm not familiar with constants. 

Would you mind showing me how you would it ?

[Bobby Eickhoff]

Depending on the component you are building its init could be a function or a constant.  StartApp doesn't require it to be a function, though a function is often appropriate.

If you're not taking any parameters, you could just define the value:

init = 0

In that case you would use it directly:

StartApp.start
  { init = init
  ...
  }

Alternatively, as you already showed, you could use always to make init a function which always returns a certain value:

init =
  always 0

In that case, you would need to pass it a (dummy) argument:

StartApp.start
  { init = init ()
  ...
  }

[Thomas Weiser]

A function that takes no arguments is a constant.

type alias Model = Int

init : Model
init = 17

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[Max Goldstein]

I'll agree with most posters that you just want to define a constant.

always is a function defined in Basics: always thing _ -> thing

You can also look at the unit type/value (). It's a type with only one value, so that value doesn't convey any information. It gets used as a placeholder.

But again, for your case, just define a constant.

[Joey Eremondi]

It is important to distinguish a function that takes no input from a function that ignores its input. "always" gives the latter, and the former is just a constant.

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[Pabich Pawel]

Thanks guys.

This is exactly what  I was looking for.