Compose multiple functions

Compose multiple functions

compose(..., .dir = c("backward", "forward"))

Arguments

...	Functions to apply in order (from right to left by default). Formulas are converted to functions in the usual way. These dots support tidy dots features. In particular, if your functions are stored in a list, you can splice that in with !!!.
.dir	If "backward" (the default), the functions are called in the reverse order, from right to left, as is conventional in mathematics. If "forward", they are called from left to right.

Value

A function

Examples

not_null <- compose(`!`, is.null)
not_null(4)
#> [1] TRUE
not_null(NULL)
#> [1] FALSE

add1 <- function(x) x + 1
compose(add1, add1)(8)
#> [1] 10

# You can use the formula shortcut for functions:
fn <- compose(~ paste(.x, "foo"), ~ paste(.x, "bar"))
fn("input")
#> [1] "input bar foo"

# Lists of functions can be spliced with !!!
fns <- list(
  function(x) paste(x, "foo"),
  ~ paste(.x, "bar")
)
fn <- compose(!!!fns)
fn("input")
#> [1] "input bar foo"