The Swiss Army Knife of Hashmaps
I read TFA discussion of performance issues for hashmaps, and I see that deletes are something of a serious hindrance.  As I often use hashmaps for a single-pass accumulation or transformation of data, I suspect that a hashmap without a delete operator might be designed to give superior performance in many such cases.  Is this so, and are there any such implementations of hashmaps, mutable but with no delete method?