Dynamic Scoping

The one unambigiously bad design choice in programming languages.

Started 17 hours ago Last edited 17 hours ago

Lexical Scoping refers to when the location of a function’s definition determines which variables you have access to. On the other hand, Dynamic Scoping uses the location of the function’s invocation to determine which variables are available.

#lang smol/dyn-scope-is-bad

(defvar y 2)
(deffun (times-2 x)
    (* y x))

(let ([y 3])
  (times-2 2))
(times-2 2)

Evaluation:

6
4

Well, this is bad.

References / Further Reading

Programming Languages Lectures

Ctrl+f for ‘dynamic scope’