On 5/30/13 8:40 AM, Tommy M. McGuire wrote:
On 05/30/2013 04:56 AM, Niko Matsakis wrote:
Another example is in Hashmaps, where we offer two variants on the
"find-or-insert" pattern:
fn find_or_insert(&mut self, K, V) -> Option<&V>
fn find_or_insert_with(&mut self, K, &fn(&K) -> V) -> Option<&V>
Under my proposal there would just be:
fn find_or_insert(&mut self, K, &fn(&K) -> V) -> Option<&mut V>
fn find_or_insert_zero(&mut self, K) -> Option<&mut V> // where V:Zero
Thoughts?
I like the idea of the closure, but (as a relative newcomer), how would
the Zero trait be specified? Wouldn't it require all HashMap's V's
implement Zero?
You can add additional bounds to type arguments for a subset of the
methods. Use a different impl block:
impl<K,V> HashMap<K,V> {
... find_or_insert goes here ...
}
impl<K,V:Zero> HashMap<K,V> {
... find_or_insert_zero goes here ...
}
Patrick
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