Why Can\'t Functions Be Used as Map Keys in This Programming Language?

Function as Map Key: A Language Restriction

Using functions as map keys, as demonstrated in the provided code snippet, raises an error due to a specific limitation in the programming language.

The error encountered, "invalid map key type Action," stems from the fact that the key type for a map cannot be a function, map, or slice. This restriction is enforced to ensure that the comparison operators (== and !=) can be fully defined for the key type.

In the given example, attempting to use the functions test and test2 as map keys violates this restriction, resulting in the error. Therefore, it is not possible to use functions as map keys in this programming language.

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