KeyMapping typedef

KeyMapping = String Function(String? str)

Often it is desirable to define equivalences between Key strings, for example for case insensitivity.

This is achieved via the surjection:

• m : S↠ K ⊆ S

such that:

• S is set of all strings
• K is set of Keys

m(m(x)) = m(x), i.e. m must be idempotent, repeated applications do not change the result.

For example:

• m(x) = lowercase(x).

KeyMapping is optionally specified during construction and applied to keys during all operations.

If no KeyMapping is supplied then the default identity function is used.

• m(x) = x.

Predefined mappings include:

• lowercase
• uppercase
• collapseWhitespace
• nonLetterToSpace
• lowerCollapse
• joinSingleLetters

If str is null then the name of the keymapping is returned.

Implementation

typedef KeyMapping = String Function(String? str);