On Friday, 6 April 2018 at 00:21:54 UTC, H. S. Teoh wrote:
On Thu, Apr 05, 2018 at 11:53:00PM +0000, Kayomn via
Digitalmars-d-learn wrote: [...]
[...]
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`lastID`, as declared above, are runtime variables. The
'static' in this case just means it's thread-local, rather than
allocated on the stack. You cannot modify these variables at
compile-time.
[...]
You appear to be wanting to increment a global variable during
compile-time. Unfortunately, there is no such thing as a
compile-time global variable. You will have to find some other
way to implement what you want.
One way to do this would be to use compile-time introspection
to construct a list of nodes, and then use a CTFE function or
static foreach to generate node IDs all at once. For example:
string generateEnum(T...)()
{
if (__ctfe) { // only run at compile-time
string code = "enum NodeIds {";
foreach (ident; T) {
code ~= ident ~ ", ";
}
code ~= "}";
return code;
}
else assert(0);
}
alias MyNodes = List!(
// Just an example; you probably want to generate this
// list via introspection, e.g. via __traits(getMembers)
// or something like that.
identifier1,
identifier2,
...
);
mixin(generateEnum!MyNodes); // defines `enum NodeIds`
static assert(NodeIds.identifier1 == 0);
static assert(NodeIds.identifier2 == 1);
...
There are probably other ways to do it too, but I chose enum
because it naturally assigns incrementing IDs to its members,
so it's a convenient construct for this purpose.
T
I think I didn't explain well enough, I'm not trying to generate
an enum from a list of pre-defined known quantities. The idea is
that a compile-time generic function exists and it generates a
unique identifier for that node.
My reasons for doing this is to remove the need to keep a master
enum that holds an identifying value for each node. I've
implemented this same thing in C++ before and it was extremely
straightforward.
