Abstract/ion

• Abstraction

  • Hiding complexity behind an interface so that higher-level reasoning can proceed without knowledge of lower-level details.

  • Levels

    • Abstraction works in layers: each level exposes a simplified model and conceals its implementation beneath it.
    • 1. A function abstracts a sequence of steps.
    • 2. A module abstracts a set of functions.
    • 3. An API abstracts an entire system.

  • Key Properties

    • Interface vs. implementation: the caller sees what something does; the abstraction decides how.
    • Information hiding: irrelevant detail is suppressed, not just renamed.
    • Composability: abstractions can be stacked — each layer need only understand the one immediately below it.

  • Relation to Declarative Style

    • Abstraction makes Declarative programming possible: to declare what should happen, there must be a layer that handles how.
    • Imperative code is often the implementation layer that a good abstraction hides.

  • Leaky Abstractions

    • An abstraction leaks when hidden implementation details escape into the interface — forcing callers to know things the abstraction was supposed to conceal.