Types in Depth

Types in Depth

In this lesson — part of Data Deep Dive — you'll learn types in depth in F# and why it matters in real work.

Why it matters

Types tell you what operations make sense and catch whole classes of bugs early.

Key ideas

• Common types: text, numbers, booleans
• Type conversion and coercion
• When to be explicit about types
• Type errors and how to read them

In practice

Here's how it looks in idiomatic F#:

// Records: immutable, structural equality, copy-and-update
type Point = { X: float; Y: float }
let p = { X = 1.0; Y = 2.0 }
let p2 = { p with Y = 9.0 }   // non-destructive update

// Discriminated unions model 'one of' choices
type Shape =
    | Circle of radius: float
    | Rect of width: float * height: float

let area = function
    | Circle r -> System.Math.PI * r * r
    | Rect (w, h) -> w * h

F# note: Discriminated unions plus exhaustive pattern matching give compiler-checked 'make illegal states unrepresentable' modelling — the compiler warns when a match misses a case.

Try it yourself

Exercise: In F#, convert a number to text and back, and print both.

Recap

You now understand types in depth and can apply it in F#. Mark this lesson complete and continue to the next one.