slide 3## Structural Definition

A fraction consists of 3 components:
- A
**sign** which is either + or -
- A
**numerator** which may be any non-negative integer
- A
**denominator** which may be any positive integer (>0)

A structural definition defines the values of a type by imposing an
internal structure on them.
Parts may be further constrained:

- Normalized representation:
- numerator and denominator must have no common divisor