On 08/02/2016 07:55 PM, Mark J Twain wrote:
It's nice to be able to pass delegates and functions as callbacks.
A nice feature is something like
R foo(R,Args...)(R function(Args) callback, Args args) { return
callback(args); }
There are two problems with this.
One is that type deduction doesn't work. I have to explicitly specify
the types of args. This creates a lot of verbosity. Second, I can't pass
ref parameters. The usefulness of this method is that it sort of lets
you pass data in and out of the callback, all defined by the user
calling foo. Sometimes you want to pass in references to store data and
other times you don't.
Is this a bug in D's type checking system or unfinished work or simply
nonsense?
right now I pass in pointers, but that doesn't work to well for some
types, and is messy.
I didn't know one could use 'auto ref' in this case but the following
simple test works:
auto foo(Func, Args...)(Func callback, auto ref Args args) {
return callback(args);
}
double bar(ref int i, int j, ref int k) {
i = 100;
k = 102;
return 7.5;
}
void main() {
int i;
int k;
auto a = foo(&bar, i, 2, k);
assert(i == 100);
assert(k == 102);
assert(a == 7.5);
}
Ali
