Associative array mutation of a value

[bearophile]

Idan Arye:

> but I don't think Erlang's idiom of using maps as records is 
> good for D.

I didn't meant to use that idiom in D, and I am not suggesting 
its usage in D. I wanted just to suggest an alternative way to 
modify associative array values that requires the keys to be 
already present. Because this is a common operation where you 
don't want to add a new key by mistake.

Bye,
bearophile