Return values from loops

[rhaiscript]

Return values from loops

[luciusmagn]

Awesome! I am very close to working modules 2017-12-01 3:17 GMT+01:00 Russ <[email protected]>:

…

just an update, i'm extremely close to getting this working 100% — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#45 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AIAzh57E1owNBb2dF5bF3fC9OQQLUhK9ks5s72HCgaJpZM4QMs2V> .

[rustysec]

so this works, but without introducing a () type into the script engine we can end up in some weird states. a loop {} may not always return something, there's no enforcement of consistency at this point. for instance a while loop like this:

let i = 0;
while i < 100 {
    if i == 50 { break true; }
    i+=<user input>;
}

depends on the user input to increment. if it never hits 50, the loop returns with () at the end which the engine doesn't really know how to gracefully handle. something like this is a simpler example:

> let x = while true == false { break; }
> print(x)
error: Function argument types do not match

while this works as expected:

> let x = while true == true { break 7 }
> print(x)
7

If anyone has ideas other than me implementing a () type, i'd love to hear them!

[schungx]

I'm wondering whether this is really necessary, as it is just as easy to write:

let x;

loop {
    // complicated computations
    x = 7;
    break;
};

This way, statements such as while, loop, for etc. do not need to be turned into valid expressions, avoiding some weird-looking scripts like let x = while true == true { break 7 };.

For Rust, it is actually useful because you need not make x mutable if you create it directly from the loop. However, Rhai variables are mutable by default and opt-out by const.

[schungx]

I'm closing this one unless that are new opinions.