Pop the Front Element

Returns the first element and the remaining sequence.

Usage

pop_front(x)

Arguments

x

A flexseq.

Value

A list with fields:

• value: the first element, or NULL when x is empty.

• remaining: the sequence after removing the first element.

Details

This operation is persistent: x is not modified.

On empty input, returns a non-throwing miss object with value = NULL and remaining = x.

Examples

s <- flexseq("a", "b", "c")
out <- pop_front(s)
out$value
#> [1] "a"
out$remaining
#> Unnamed flexseq with 2 elements.
#> 
#> Elements:
#> 
#> [[1]]
#> [1] "b"
#> 
#> [[2]]
#> [1] "c"
#> 
s  # unchanged
#> Unnamed flexseq with 3 elements.
#> 
#> Elements:
#> 
#> [[1]]
#> [1] "a"
#> 
#> [[2]]
#> [1] "b"
#> 
#> [[3]]
#> [1] "c"
#> 

pop_front(flexseq())
#> $value
#> NULL
#> 
#> $remaining
#> Unnamed flexseq with 0 elements.
#>