Define constants

[bbaldino]

Wondering if there'd be any interest in defining constants for all values for each of the types. I have been playing with this for packet parsing, and there's often a field that corresponds to a fixed set of packet types that it would be handy to be able to use constants for.

struct MyPacket {
    ...
}

impl MyPacket {
    pub const TYPE: u4 = u4::C10; // The value '10' in a u4
}

fn parse(...) {
    let type: u4 = ...
    match type {
        MyPacket::TYPE => { ... },
        OtherPacket::TYPE => { ... },
        // etc
    }
}

[kjetilkjeka]

I like the idea. But this is >10^40 constants, I imagine this would be a problem for both the rust compiler in terms of the amount of symbols and the recursion depths of the macros required to write out all these constants. Am I wrong here? Are there any smart ways to only having to define the constants actually in use?

I see that panic is also supported in const context now. There is no reason for not making new a const function. Would that solve the problem?

[bbaldino]

But this is >10^40 constants, I imagine this would be a problem for both the rust compiler in terms of the amount of symbols and the recursion depths of the macros required to write out all these constants.

Good point...when I played around with this in my own lib I only supported up to u7, so this would probably be a bit much.

I see that panic is also supported in const context now. There is no reason for not making new a const function. Would that solve the problem?

Yeah I hadn't thought about that but that would work fine!