accumulate_while: Accumulate a list by iteratively performing a function
In dgrtwo/drlib: Personal R package of David Robinson

Description Usage Arguments Details Examples

Perform a function to transform an object multiple times, until a predicate is not satisfied.

1	accumulate_while(.x, .f, .p, ..., .compare = FALSE, .max = 1e+05)

`.x`	Starting value
`.f`	Function to apply to transform each step to the next
`.p`	A predicate applied to each intermediate step: if false, it stops the iteration
`...`	Extra arguments passed to .f
`.compare`	Whether the predicate will be given the last two steps rather than just the most recent.
`.max`	Maximum number of iterations to perform. Give `Inf` to continue growing the vector as long as necessary.

I've suggested a function like this in an issue on purrr: https://github.com/hadley/purrr/issues/253. I've put it here so I can use it personally in the meantime. If it gets added to purrr, I will remove it from drlib.

accumulate_while(1, ~ . + 1, ~ . < 5)

# accumulate until difference is within some tolerance
accumulate_while(1, ~ . / 2, ~ abs(.x - .y) > 1e-4, .compare = TRUE)