$: Self-Reference

>> << Ndx Usr Pri Phr Dic Rel Voc !: wd Help Dictionary

Self Reference | $: _ _ _ |

`$:` denotes the longest verb that contains it. For example:
       1:`(] * $:@<:)@.* 5
    120
In the foregoing expression, the agenda`` (`@.`)`` chooses the verb`] * $:@<:` as long as the argument (reduced by one each time by the application of the decrement) remains non-zero. When the argument becomes zero, the result of the right argument of`@.` is zero, and the constant function`1:` is chosen. If`$:@` were omitted from the expression, it would execute once only as follows:
       1:`(] * <:)@.* 5
    20
The inclusion of self-reference ensures that the entire function is re-executed after decrementing the argument. `v f.` will not fix any part of`v` that contains`$:` .

>> << Ndx Usr Pri Phr Dic Rel Voc !: wd Help Dictionary