Iterator that drops elements until the predicate function returns FALSE

Constructs an iterator that drops elements from the iterable object as long as the predicate function is true; afterwards, every element of iterable object is returned.

Usage

i_dropwhile(object, predicate, ...)

Arguments

object

an iterable object

predicate

a function that determines whether an element is TRUE or FALSE. The function is assumed to take only one argument.

...

Further arguments forwarded to iteror.

Value

An iteror object.

Details

Because the iterator does not return any elements until the predicate first becomes false, there may have a lengthy start-up time before elements are returned.

Examples

# Filters out numbers exceeding 3
not_too_large <- function(x) {
  x <= 3
}
it <- i_dropwhile(1:8, not_too_large)
as.list(it)
#> [[1]]
#> [1] 4
#> 
#> [[2]]
#> [1] 5
#> 
#> [[3]]
#> [1] 6
#> 
#> [[4]]
#> [1] 7
#> 
#> [[5]]
#> [1] 8
#> 

# Same approach but uses an anonymous function
it2 <- i_dropwhile(seq(2, 20, by=2), function(x) x <= 10)
as.list(it2)
#> [[1]]
#> [1] 12
#> 
#> [[2]]
#> [1] 14
#> 
#> [[3]]
#> [1] 16
#> 
#> [[4]]
#> [1] 18
#> 
#> [[5]]
#> [1] 20
#>