Types in Depth

Types in Depth

In this lesson — part of Data Deep Dive — you'll learn types in depth in Haskell 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 Haskell:

-- Algebraic data types plus a type alias; constructors build values
type Name = String
data Shape = Circle Double | Rect Double Double

area :: Shape -> Double
area (Circle r)   = pi * r * r
area (Rect w h)   = w * h

Haskell note: Types are erased at runtime and inferred globally via Hindley–Milner, so most annotations are optional documentation rather than a requirement for compilation.

Try it yourself

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

Recap

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