📦 Product Types

Theory

A product type bundles multiple values together (“and” data).

Tuples

type Point = (Double, Double)

Records

data Circle = Circle
  { cx :: Double
  , cy :: Double
  , r  :: Double
  }

Pattern‑match or use field selectors: r circ.

Semantics

If A has $|A|$ values and B has $|B|$ values, then $(A,B)$ has $|A|\times |B|$.

Implementation

Constructors combine, patterns split:

area :: Circle -> Double
area (Circle _ _ rad) = pi * rad * rad