dapper nest
given this struct:
pub fn GenericType(comptime T: type) type {
return struct {
field1: T,
pub fn init(field1: T) @This() {
return .{ .field1 = field1 };
}
};
}
how could i return this struct in a function, without the type specified, for instance:
pub fn doAThing(...) GenericType {
...
}
dull nimbus
Here GenericType is a name of a function, so you can't return it as a type/struct.
But GenericType(<type>) is a type, so you could do
pub fn doAthing(...) GenericType(<type>) {...}
shut scarab
If the desired behavior of not specifying the type is for it to be inferred, instead you could do something like
fn DetermineType(...args) type {
// determine what type doAThing will return based on some logic
}
pub fn doAthing(...args) GenericType(DetermineType(...args)) {...}
DetermineType will only be able to look at comptime args though
dull nimbus
Yes that's possible.
shut scarab
You can't in general have a type be known only at runtime
dull nimbus
Yes since types only exist in comptime and can only depend on comptime knowns.
dapper nest
hmm
this is a bit of a problem i guess
because i cannot specify the type at compile time
what could be a solution
dapper nest
the problem is that it should be able to be any possible type
is there anyway that i could have a value be any type at run time?
shut scarab
Not in a way that lets you remember the type
Depending on the use-case, it might still be possible to do what you're doing, but there are infinite types and code cannot be infinitely big
Like for generic functions, Zig creates a different function for each type argument so that there is no type information at runtime. In order for this to be possible, the set of type inputs that function is called with must be known at compile time
You can't have generic functions that are instantiated for every possible type
dapper nest
so there is no void * equivalent for zig?
fringe iron
that's how void * works
fringe iron
not with as
fringe iron
const typed: *NewType = @ptrCast(@alignCast(opaque));
fringe iron
casts from a type with one alignment to another
dapper nest
okay got it