CompareDataFunc

Specifies the type of a comparison function used to compare two values. The function should return a negative integer if the first value comes before the second, 0 if they are equal, or a positive integer if the first value comes after the second.

• param a a value

• param b a value to compare with

• return negative value if @a < @b; zero if @a = @b; positive value if @a @b