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Programming-Idioms

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  • Scala

Idiom #140 Delete map entry

Delete from map m the entry having key k.

Explain what happens if k is not an existing key in m.

m - k

The map m is not mutated, and a new map is returned instead. If k doesn't exist in m, no error occurs. The default implementation of Map is a HashMap.
m -= k

This mutates the map m, removing k from it. If k doesn't exist in m, no error occurs. Only available on mutable Map. The default implementation of Map is a HashMap.
(dissoc m k)

Returns a new map without the key k. If k doesn't exist the original map is returned unaltered.
New implementation...
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programming-idioms.org 
m - k
m -= k
(dissoc m k)
m.erase(k);

map.Remove(key);
m.remove(k);
Map myMap = {};
myMap.remove(key)
m = Map.delete(m, k)
delete(m, k)
delete k m
m.delete(k)
map.remove(k);
m[k]=nil
unset($m[k]);
m.delete(k);
delete $m{$k}; # also succeeds when $k does not exist in %m
m.pop(k, None)
m.delete(k)
m.remove(&k);