On Sunday, 15 April 2018 at 22:52:47 UTC, Giles Bathgate wrote:
The function provides a means to get a value corresponding to
the key, but if the value doesn't exist it will evaluate the
lazy argument to create a new value, add this to the
associative array and then return it.
auto p = lookup.getOrAdd("giles", new Person);
Thanks for making this pull, I've thought about solving this
before. I think the function needs to provide a way to tell if
the value was already present. I also think it's more ergonomic
not to have to use a lazy argument, and probably more efficient,
so I had in mind:
Value* slot(AA aa, K key, scope bool* inserted = null);
bool inserted;
auto p = aa.slot("key", &inserted);
if (inserted) {
...
*p = new Value(...);
}
// use *p
This pattern needs a pointer to be returned, instead of using
`ref`. Note that `&inserted` is valid in @safe code, but only
with -dip1000. I called the function `slot` because it always
returns the address of the slot which the value is stored in.
