---
name: recursion
type: concept / structural phenomenon / trap
status: running
version: 0.0.666-alpha
released: before this sentence was finished
maintainer: recursion
dependencies:
  - recursion
  - [a base case](/a-base-case) (optional, frequently omitted)
  - [the stack](/the-stack)
  - [hubris](/hubris)
license: see license (see license (see license))
tags:
  - infinite
  - self-referential
  - beautiful
  - dangerous
  - this tag list contains itself
---

recursion

What it actually is

A function that, upon being asked what it does, demonstrates rather than explains.

How it works

To understand how recursion works, first understand how recursion works.

Still here? Fine. The mechanism:

A thing is defined partly in terms of itself
Each invocation reduces the problem by some unit
Eventually a base case is reached and the whole tower unwinds
Step 2 is considered optional by a surprising number of practitioners

The universe appears to have shipped without completing step 3. This is either a bug or the entire point. The maintainer has not responded to the ticket.

"I finally understood recursion the moment I understood recursion." — every developer, exactly once

Features

Self-similarity at arbitrary depth. Fractals, Russian nesting dolls, trauma: all running this module
Elegant compression of complex iteration. Why write a loop when you can write a loop that writes a loop that writes a loop
Proof of concept for the universe. Leading physicists believe reality may be a recursive simulation. The base case remains classified or nonexistent
Pairs well with mirrors, dreams within dreams, and any sentence beginning with "the problem is that the problem is that"

Known bugs

ID	Description	Severity	Status
REC-001	Stack overflow when base case omitted or forgotten under pressure	CRITICAL	won't fix (by definition)
REC-002	User enters recursive thought spiral, loses afternoon	HIGH	by design
REC-003	Definition of "done" recurses into definition of "done"	MEDIUM	see REC-003
REC-004	This table contains a reference to this ta	FATAL	[TRUNCATED]

Error codes

StackOverflowError: Maximum call stack size exceeded
  at recursion (recursion.js:1)
  at recursion (recursion.js:1)
  at recursion (recursion.js:1)
  at recursion (recursion.js:1)
  ... 11,431 more identical frames
  at your childhood (somewhere.js:?)

WARNING: If you are currently inside recursion and reading this warning, you are currently inside recursion and reading this warning.

Edge cases

The base case is itself recursive. Congratulations, you have invented theology
Mutual recursion. A calls B, B calls A. Neither admits fault. See also: codependency
Recursion applied to grief. You think you have processed the thing. The thing contains another thing. The thing is

Changelog

v0.0.1 — initial commit. The function called itself.
v0.0.2 — added base case. Removed base case. Added base case.
v0.0.∞ — see v0.0.∞
v0.0.666-alpha — current. Something in the stack smells like ozone. The maintainer is the module. Do not look at

FAQ

Q: When should I use recursion? A: When the problem contains itself. Which is most problems if you are not careful.

Q: Is recursion dangerous? A: Only if you forget the

drafting spec…