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64.3.4 The category ‘comparable’

Deductively, the category of comparables are all numbers which possess a total (archimedean) order. Inductively, this category is the union of reals and rationals. Comparables, as the names suggests, can be directly compared with ordering relations, such as < or >.

The category's predicate is comparablep.

— Function: comparablep object

Return t if object is comparable (i.e. a real or a rational), nil otherwise.

We call a number comparable if there exists a total (archimedean) order on the underlying structure. 

     (comparablep 0)
          ⇒ t
     (comparablep 1/2)
          ⇒ t
     (comparablep 0.5)
          ⇒ t