Rust Programming

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Which is faster? (lemmings.world)

submitted 1 week ago* (last edited 1 week ago) by [email protected] to c/[email protected]

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let mut variable: Type;
loop {
    variable = value;
}

loop {
    let variable: Type = value;
}

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[+] [email protected] -17 points 1 week ago (3 children)

The second one is more expensive as you constantly are creating a new variable. In the first one you just constantly change the value of a variable.

[–] [email protected] 12 points 1 week ago* (last edited 1 week ago)

This is Rust not Python

They're both optimised out by the compiler. If you disable compiler optimisations, they're identical in machine code anyway, unless you introduce a second loop, in which case the first will be more memory efficient as the memory used in the first loop can be reused in the second loop, whereas if you declare the variable outside the loop it can't (again, without compiler optimisations, which make the whole comparison pointless).

[–] [email protected] 10 points 1 week ago

This is just flat out false.