urbit/pub/docs/dev/hoon/runes/cl/clcb.md

colcab, :_, %clcb

Cell, backwards

:_, colcab, [%clcb p=twig q=twig] is a synthetic rune that produces the cell [q p].

Produces

Twig: [%clcb p=twig q=twig]

Sample

p is a twig. q is a twig.

Tall form

:_  p
    q

Wide form

:_(p q)

Irregular form

undefined

Examples

~zod/try=> :_(1 2)
[2 1]

A simple example. :_ produces the cell of any two twigs, but in reverse order.

~zod/try=> `tape`:_(~ 'a')
"a"

Since a ++tape is a null-terminated list of characters, casting the result of :_(~ 'a') to a tape produces "a".

/~zod/try=> 
    :_  (add 2 2)
    |-  (div 4 2)
[2 4]

Most commonly :_ helps to organize code, allowing you to produce a cell from nested computation.