A value boxed with done()
signals to its caller that it
should stop iterating. Use it to shortcircuit a loop.
done(x)
is_done_box(x, empty = NULL)
For done()
, a value to box. For is_done_box()
, a
value to test.
Whether the box is empty. If NULL
, is_done_box()
returns TRUE
for all done boxes. If TRUE
, it returns TRUE
only for empty boxes. Otherwise it returns TRUE
only for
non-empty boxes.
A boxed value.
done(3)
#> <done>
#> [1] 3
x <- done(3)
is_done_box(x)
#> [1] TRUE