How would it be different from defining a default constructor?
Structs
specifically _don't_ have default constructors, because init
must be known at
compile time, and all kinds of restrictions would have to be
placed on a
default constructor (enough to make it pointless) to ensure
that it would work
as an init value that there's really no point to it. The kind
of stuff that
you'd want to do in a default constructor but can't do by
directly
initializing the member variables is precisely the kind of
stuff that you
_can't_ do with a struct, because init must be known at compile
time, must
always generate the same result, couldn't throw exceptions, etc.
So, sure, at times it would be great to have a default
constructor for
structs, but other design decisions in the language
(particularly with regards
to init) simply make that infeasible. It's one of those "forced
faults" in
language design that Andrei likes to talk about.
So, what we get is an init value defined by how the member
variables are
directly initialized and the ability to define a static opCall
to get you the
equivalent of the default constructor in cases where S() is
used rather than
S.init. It's not perfect, but there's not much that we can do
about it.
- Jonathan M Davis
My idea was to declare your own .init in a class, not in a struct.
