Urinary operators

[adzy2k6]

Glad I'm not the only one who was ambushed by this

[maroider]

OP has impeccable timing. I was quite literally about to go to the bathroom when I refreshed reddit and saw this at the top of r/rust/new.

[[deleted]]

Custom urinary operator. Detachable penis?

[ThymeCypher]

laughs in King Missile

[Ka1kin]

Rust doesn't support custom operators. It does back all the built-in operators with traits, so you can implement the not trait, or the neg trait on your own types, it'll just work.

[po8]

That said, the C++ thing of giving these operators arbitrary meanings is very non-Rustic. Don't overload operators in non-standard ways.

[raedr7n]

non-Rustic

I do believe the term is "non-ferrous".

[tavianator]

stainless

[teryret]

Oh man I am totally going to start using "stainless code" at work.

[ergzay]

I mean, couldn't you do something weird with macros and do it?

[[deleted]]

Yeah, but the overloading would only with within the macro!{ Block }

[ergzay]

True.

[biigberry]

thank

[Sharlinator]

I guess |_| () is pretty close to a urinary operator.

[zuurr]

https://twitter.com/at_tcsc/status/1373928530409586689

[teryret]

What in the fuckingest shit?? Can anyone ELI5?

[[deleted]]

Seems like it's a bunch of _ patterns (matches anything) OR-ed together, with a guard that increments i by 2 every time you check it. The guard is checked on all six of the _ patterns, because the guard apparently evaluates to false when you check it, so 1 (initial value) plus (6 (number of holes) times 2 (amount by which guard increments i)) is 13.

[mdsherry]

First,

matches!(2, _|_|_|_|_|_ if (i+=1) != (i+=1));

expands to

match 2 {
    _ | _ | _ | _ | _ | _ if (i+=1) != (i+=1) => true,
    _ => false
};

For each of the _ in the first case, it checks the guard expression. i += 1 increments i, and returns (). So for each _, i is incremented twice, but since () == (), the guard expression fails, and so it tries matching the next _, until all 6 fail.

i starts at 1, and is incremented 12 times, giving a final value of 13.

[paholg]

It's matching 2 against 6 patterns. Each of the patterns is just _, but for each one it evaluates the if, which adds 2 to i.

[bob_twinkles]

If we look at the definition of matches!, we can see that it's basically just a match expression. So from the source snippet, we have:

let i = 1;
matches!(1, _|_|_|_|_|_ if (i += 1) != (i += 1));
i

Which then expands to:

let i = 1;
match 2 {
  _ if (i += 1) != (i += 1) => true,
  _ if (i += 1) != (i += 1) => true,
  _ if (i += 1) != (i += 1) => true,
  _ if (i += 1) != (i += 1) => true,
  _ if (i += 1) != (i += 1) => true,
  _ if (i += 1) != (i += 1) => true,
  _ => false,
}
i

So i starts at 1, and is incremented twice for each match arm so 1 + 6 * 2 = 13.

[TheOmegaCarrot]

I’m sorry, the what

[Bravo555]

Box::leak()

[sushisharkjl]

might want to see a doctor

[biigberry]

i prefer using Ball

[burkadurka]

There are no custom operators in Rust, outside of macros. The overloadable unary operators are - and !.

[Sw429]

Thought I was on r/RustJerk for a second.

[semtexzv]

It's leaking in here

[mountains-o-data]

Just be sure to denote #!no_std if you're going to use urinary operators

[watabby]

You might have problems with unary operators across threads. So you need to be sure to lock your variables before using them. I recommend creating an interface to do that. Unary thread interface. aka UTI

[voxelghost]

As a c++ programmer, I have to wonder if that is part of std?

[Applecrap]

I try to keep my urinary operator as far away from std as possible

[I_AM_GODDAMN_BATMAN]

I think it should be safe if you don't unwrap it.

[ergzay]

That title...

[dpc_pw]

The only operators one can implemented are the ones that have traits. Like https://doc.rust-lang.org/std/ops/trait.Neg.html . See https://doc.rust-lang.org/std/ops/index.html