Thun/docs/reference/loop.md

Basis Combinator Expect a quoted program `Q` and a Boolean value on the stack. If the value is false discard the quoted program, otherwise run a copy of `Q` and `loop` again. false [Q] loop

## loop Basis Combinator Expect a quoted program Q and a Boolean value on the stack. If the value is false discard the quoted program, otherwise run a copy of Q and loop again. false [Q] loop

   true [Q] . loop
--------------------------
            . Q [Q] loop

Discussion

This, along with [branch] and [fork], is one of the four main combinators of all programming. The fourth, sequence, is implied by juxtaposition. That is to say, in Joy F G is like G(F(...)) in a language bassed on function application. Or again, to quote the Joy Wikipedia entry,

In Joy, the meaning function is a homomorphism from the syntactic monoid onto the semantic monoid. That is, the syntactic relation of concatenation of symbols maps directly onto the semantic relation of composition of functions.

Anyway, [branch], [fork], amd [loop] are the fundamental combinators in Joy. Just as [branch] has it's more common and convenient form [ifte], [loop] has [while].

Crosslinks

[branch] [fork] [while]