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Variable swapping (without a temp variable)

Problem

You have two variables and want to swap their values cleanly—without introducing a temporary variable.

Idiom: Redeclare with list decomposition

Slug lets you destructure lists, and (in the right scope) redeclare variables. Combine those to swap in one expression:

  • Build a pair [a, b]
  • Destructure it back into the opposite order [b, a]

Recipe

1) Swap two variables in-place

var {*} = import("slug.test")

var a = 1
var b = 2

// swap via list decomposition (no temp variable)
var [b, a] = [a, b]

a /> assertEqual(2)
b /> assertEqual(1)

2) Works with any values (not just numbers)

var {*} = import("slug.test")

var left  = "L"
var right = "R"

var [right, left] = [left, right]

left  /> assertEqual("R")
right /> assertEqual("L")

Notes

  • This pattern relies on (1) list decomposition and (2) redeclaration in the current scope.