Comment by eikenberry

Comment by eikenberry 15 hours ago

Function coloring is specifically about requiring syntax for a function, eg. the async keyword. So if you want an async and non-async function you need to write both in code. If you pass the "coloring" as an argument you avoid the need for extra syntax and multiple function definitions and therefor the function has no color. You can solve this in various ways with various tradeoffs but as long as there is a single function (syntactically) is all that matters for coloring.

woodruffw 14 hours ago

> Function coloring is specifically about requiring syntax for a function, eg. the async keyword.

Someone should tell the inventor of the phrase, because they don't mention the async keyword at all[1]. As-written, function coloring is about callbacks (since that's semantic mechanism that JavaScript happens to pick for their asynchronous model).

Function coloring is just an informal way to describe encoding a function's effect. You can encode that in syntax if you want (an `async` keyword), or in the type system (returning `() -> T` instead of `T`), or in the runtime itself (by controlling all I/O and treating it the same). But you can't avoid it.

[1]: https://journal.stuffwithstuff.com/2015/02/01/what-color-is-...

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eikenberry 13 hours ago
They specifically called it out as a syntactical issue, where the issue was based around the requirement to have the 'red' or 'blue' keyword. The section on "2. The way you call a function depends on its color." makes this pretty explicit...
2. The way you call a function depends on its color. Imagine a “blue call” syntax and a “red call” syntax. Something like: doSomethingAzure()blue; doSomethingCarnelian()red; When calling a function, you need to use the call that corresponds to its color.
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- woodruffw 11 hours ago
  
  I don’t think so? The implication is that it’s a callback, which of course is going to require another call to realize the evaluation. But it’s not inherently another keyword; the keyword is just sugar for deferred evaluation.
  
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IshKebab 15 hours ago

> Function coloring is specifically about requiring syntax for a function, eg. the async keyword.

It isn't really. It's about having two classes of functions (async and sync), and not being able to await async functions from sync ones.

It was originally about Javascript, where it is the case due to how the runtime works. In a sync function you can technically call an async one, but it returns a promise. There's no way to get the actual result before you return from your sync function.

That isn't the case for all languages though. E.g. in Rust: https://docs.rs/futures/latest/futures/executor/fn.block_on....

I think maybe Python can do something similar but don't quote me on that.

There's a closely related problem about making functions generic over synchronicity, which people try and solve with effects, monads, etc. Maybe people call that "function colouring" now, but that wasn't exactly the original meaning.

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