head_while: Find head/tail that all satisfies a predicate.
Description
Find head/tail that all satisfies a predicate.
Usage
head_while(.x, .p, ...)
tail_while(.x, .p, ...)
Arguments
.x
A list or vector.
.p
A single predicate function, a formula describing such a
predicate function, or a logical vector of the same length as .x.
Alternatively, if the elements of .x are themselves lists of
objects, a string indicating the name of a lo