purrr (version 0.3.4)

compose: Compose multiple functions

Description

Compose multiple functions

Usage

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

Value

A function

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.

Examples

not_null <- compose(`!`, is.null)
not_null(4)
not_null(NULL)

add1 <- function(x) x + 1
compose(add1, add1)(8)

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

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