# Why quotient and subset on datatype ?

Why we need quotients and subsets of datatypes ?

One of the reaons is we could derive operations naturally. A simple example is the unordered pair. Define $R_{uo}$ as $(a, b)~R_{uo}~(b, a)$ for all $a, b \in \mathbf{A}$. Then, $(\mathbf{A} \times \mathbf{A}) / R_{uo}$ is the unordered pair. Continue reading