I'm making a macro to iterate over any tuple of components in my ECS.
In the main lines, here is how it goes :
for (pos: &Position, vel: &Velocity) in iterate_over_components!(components; Position, Velocity) {[...]}
Where Position and Velocity are structs.
For now, I'm having two iterator: a immutable one and a mutable one. I would like to merge them into one, specifying which components are mutable.
for (pos: &mut Position, vel: &Velocity) in iterate_over_components!(components; mut Position, Velocity) {[...]}
Currently, the rule is parsed like this :
($components:expr; $($comp:ident),+) => {[...]}
And I match the different components like so :
$(
$comp,
)+
Do I have a way to read any mut keyword in front of my declarations of multiple components ? How do I change the generated code depending on the presence of such a keyword ?
I've seen here that I would need a separate rule to match both, but in my case I don't know what components will be mutable, so I would like a way to change the generated code accordingly.
If any one want to take a look, here is the full macro, in the ECS lib.
Some edits after looking throught TT-munching :
I'm trying to pass each component or mut component as tt, but I still can't match other macros. A simple example :
#[macro_export]
macro_rules! get_component {
($components:expr; mut $comp:ident) => {
"mut".to_string()
};
($components:expr; $comp:ident) => {
"imm".to_string()
};
}
#[macro_export]
macro_rules! get_components {
($components:expr; $($comp:tt),+) => {
{
$(
get_component!($components; $comp);
)+
}
}
}
Can't match :
get_components!(&mut world.components; Component1, mut Component2);
I'm having an error on Component2 :
no rules expected the token Component2
while trying to match ,
