Unconstrained Sets

Unconstrained sets allow the user to disable one of the views of a bimap. Doing so makes the bimap operations execute faster and reduces memory consumption. This completes the bidirectional mapping framework by including unidirectional mappings as a particular case.

For example, the following code creates a type that is similar to a regular std::map.

typedef bimap< int, unconstrained_set_of< string > > bm_type;

bm_type b;
b.left[1] = "one";
b.left[2] = "two";

Unconstrained sets are useful for the following reasons:

A bimap type has stronger guarantees than its standard equivalent, and includes some useful functions (replace, modify) that the standard does not have.
You can view the mapping from above as a set of relations.
Using this kind of map makes the code very extensible. If, at any moment of the development, the need to perform searches from the right side of the mapping arises, the only necessary change is to the typedef.