This is just a brain-dump. I find the convention of putting a ! in a function name to indicate a parameter might get changed to be less than satisfactory. Because consider this change!(a, b). What if the function changes b but not a? What if it changes both a and b? There’s no way to indicate that…

[image] xiaodai: function change(a, !b) only mutates b and function (!a, !b) Unlike function names, argument names in the definition are not visible in the function call, so it’s a much worse hint. Maybe it’s not a hint at all because we have to actually look up the function, figure out its d…

Some time ago I proposed using change(a!, b) (or change2(a, b!)) to indicate what was getting changed. It is perfectly legal to use right now.

Ah nice one. Putting it in the back makes sense and is not breaking.

[image] Benny: If I really needed to indicate what gets mutated throughout my code, it should be apparent in the variable name or a comment. If I for some reason want an indication on every variable, there’s no need to change the parser to allow leading ! because I can just append any number of …

[image] xiaodai: No need to sound harsh. Makes me feel stupid. Like “why would u even do that?!” I don’t understand why you had such a negative reaction to the exact same suggestion as that offered by the following comment. If it was my inability to imagine a reason for a convention marking v…

On a tangent, I wish we had gone the route of functions appended with ? return a boolean. Allow ? in identifiers opened 04:51PM - 07 Jan 13 UTC (UTC) closed 11:45PM - 08 Jan 13 UTC (UTC) …

I like the way Swift does it, but I am aware that Julia can’t adopt it. func doubleInPlace(number: inout Int) { number *= 2 } var myNum = 10 doubleInPlace(number: &myNum) inout parameters - a free Hacking with Swift tutorial Learn Swift coding for iOS with these free tutorials …

[image] xiaoxi: I like the way Swift does it, but I am aware that Julia can’t adopt it. This is a bit different — this is to pass an argument by reference, so that you can mutate the binding of the argument when the argument is otherwise an immutable value. It’s not needed, even in Swift I b…

It’s possible we can do this without breaking the language with better tooling! I can imagine a world in which the ? help menu, or docs in general can query the mutation of various arguments. Then our documentation and other tooling can display mutation in some way (highlighting, inserting a grayed…

A possible change for Julia 2.0: per-argument mutation ! marks?

Internals & Design

stevengj September 20, 2024, 12:30am 2

That would be such an enormous change to how the language works that I think this applies: PSA: Julia is not at that stage of development anymore

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A possible change for Julia 2.0: per-argument mutation ! marks?

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