SSCCE for the entire Elm syntax

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For some reason, I was curious to see how a Short, Self Contained, Correct Example of the entire Elm syntax would look like.

I started with the counter example and added things as they came to my mind making sure to elm-format after each change. This is the result.

Did I missed any piece of syntax?

What would you add? What would you take away? What would be your take on a minimal example of the entire syntax?

How would you change the comments so that is easier to understand. (I tried to keep the comments to a minimum).

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Nice! Seems useful to me. What about record extension?

What is your goal for this, btw?

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Cool!

  • Should there be an example of destructuring in let in? let (Foo foo) = bar
  • Should there be a toplevel definition without a type annotation?
  • And a let in with a type definition? Maybe also one where a “type variable is re-used from the parent function type annotation” (I think that’s a thing).
  • Maybe a multi-line type annotation?
  • Is there any formatting we want to add, that elm-format does not output? Such as single-line if.
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Good Point. Maybe a phantom type too.

It’s just playing. No serious goals here. I sometime get questions in my mind that I would like answered. I guess I do am interested in how low can one go. Can all these things be expressed in less code? :slight_smile:

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I have produced a new version integrating the suggestions that were easier to think through.

  • Is there any formatting we want to add, that elm-format does not output? Such as single-line if.

I love the uniformity of elm-format and I would like the example to stay formatted. But you have a good point here. I know that Evan publishes code that has unconventional formatting ( like this section ) and single line ifs that fit into the line width limit are one of the things I wish elm-format would allow.

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There are some weirder bits of Elm syntax:

  • WebGL literals (technically this could inflate the example considerably since Elm subsumes most, but not all GLSL syntax).
  • The syntax used internally like effect managers / kernel code (not sure there would be much value in this)
  • There are various phantom type/extensible record tricks. Some of these were first popularised by elm-css.
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I would rather stay away from the private API of the runtime as this is not available for regular users.

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Cool! Wish this existed years ago already! This is the relevant AST if you want to make sure you’ve covered everything: https://github.com/elm/compiler/blob/master/compiler/src/AST/Canonical.hs

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This will be great for stress-testing elm-in-elm, thanks @pdamoc!

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Should << be there as well?

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I have extended the example to cover extensible records, phantom types and the WebGL shaders language.

For phantom types and the shader language I just left the code as dead code.

I have also moved the code into a github repository.

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I like the idea.

From a quick glance, it seems that at least the following are missing:

  • multiline strings (with """)
  • tuples and unit type pattern matching
  • exposing (..) import
  • characters (Char with ')
  • records fields accessors without the syntax suggar (.field record)

You could also show that record fields accessors work on expressions, for example:

(named "myname").name

Also have a look there:

There are other things like multiple imports using the same alias.

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I have updated the example to cover the things you pointed at.

I just added dead code to exemplify some of the things.

LATER EDIT: I also added an example for Debug.log usage and for multiple declarations for _.

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Seems like a cool resource to point people to if they want to get a pretty thorough overview of Elm syntax! A couple potential additions:

  • An example of partial function application
  • An example of using an operator as a function, either in prefix form like
    three =
    (+) 1 2
    or perhaps as an argument to a higher-order function, e.g.
    sums =
    List.map2 (+) [ 1, 2, 3 ] [ 10, 20, 30 ]
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I have updated the example with your suggestions.

It is very funny how I missed partial application as this is something I do all the time. Using infix operators in higher order functions is less frequent in my code but still… I use it from time to time. The use-case for infix operator as prefix function that I have in my code is actually partial application of the operator.

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This is great! I’ve seen a lot of people new to Elm ask for this sort of document, thank you for making it.

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keep in mind that you’ll be missing glsl and the internal apis like infix

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