Question

I am trying to round up cases when it makes sense to use a map (set of key-value entries). So far I have two categories (see below). Assuming more exist, what are they?

Please limit each answer to one unique category and put up an example.

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Property values (like a bean)

age -> 30
sex -> male
loc -> calgary   

Presence, with O(1) performance

peter -> 1
john  -> 1
paul  -> 1

Answer 1

If your language allows both associative arrays and pointer to functions/procedures, you can use maps to build something similar to Object Oriented (see Perl for a classical example).

See here for a more detailed explanation.