cpp/concepts/totally ordered

@1@ The concept specifies that the comparison operators  on a type yield results consistent with a  on the type.

@2@ The concept specifies that the comparison operators  on (possibly mixed)  and  operands yield results consistent with a strict total order. Comparing mixed operands yields results equivalent to comparing the operands converted to their common type.

@3@ The exposition-only concept specifies that a value of type  and a value of type  can be compared in a partial order with each other (in either order) using, , , and , and the results of the comparisons are consistent.

Semantic requirements
These concepts are modeled only if they are satisfied and all concepts they subsume are modeled.

@1@ is modeled only if, given lvalues,  and  of type :
 * Exactly one of, and  is ;
 * If and  are both, then  is ;

@2@ is modeled only if, given and let be :
 * any lvalue of type, and
 * any lvalue of type ,

@3@ is modeled only if given the following are true:
 * any lvalue of type, and
 * any lvalue of type ,
 * ,, , , , , , and have the same domain;
 * ; and
 * ; and
 * ; and