SIGNATURE SetMap[from ,< :from ** from -> bool, to, < :to ** to -> bool]

-- mappings of sets

-- Parameter
SORT from to

FUN < : from ** from -> bool
FUN < : to ** to -> bool
        -- total strict-order; in 
        --   ~(x < y) AND ~(y < x) => x = y
        -- should = represent semantic equality

IMPORT Set[from, <] ONLY set
       Set[to, <]   ONLY set

FUN * : (from -> to)** set[from, <] -> set[to, <]                       
        -- f * s
        -- apply f to all elements of s