Module:Yesno/doc

Yesno is a function that converts various "affirmative" and "negative" inputs in modules into booleans; "yes", "Y", 1 "true", "t" and "on" are all converted into a true boolean, and "no", "N", 0, "false", "f" and "off" are converted to a false boolean. This is for consistent treatment of boolean-like wikitext input.