urbit/base/pub/doc/hoon/runes/sg/sgwt.md

sigwut, ~?, %sgwt

Conditional printf

~? is a synthetic rune with the same hint effect as ~&, printing r if and only if q produces &, loobean yes.

Produces

Twig: [%sgwt p=@ud q=twig r=twig s=twig]

Sample

p is a @ud. q is a twig. r is a twig. s is a twig.

Tall form

Priority 0 (debug):

    ~&  q
    r

Priority 1 (notice):

    ~&  >  q
    r

Priority 2 (warning):

    ~&  >>  q
    r

Priority 3 (alarm):

    ~&  >>>  q
    r

Wide form

~&(>> q r)

Irregular form

None

Examples

~zod/try=> ~?((gth 1 2) 'oops' ~)
~
~zod/try=> ~?((gth 1 0) 'oops' ~)
'oops'
~

A simple case of the conditional printf. When our condition evaluates to & we print our r. Most useful in computation dealing with dynamic data.