Package {functional}

Compose an arbitrary number of functions.

Description

My Happy Hacking keyboard gave out during the writing of this procedure; moment of silence, please.

Usage

Compose(...)

Arguments

Details

Had to make this slightly more complex to handle the nullary case; also included a fast-path for the trivial case.

Value

A composed function

Examples

car <- function(list) list[[1]]
cdr <- function(list) list[2:length(list)]
cadr <- Compose(cdr, car)
stopifnot(cadr(c(1,2,3)) == 2)

Pre-specify a procedures named parameters, returning a new procedure.

Description

Thanks, Byron Ellis; and Aaron McDaid modified it to preserve names across invocation.

Usage

Curry(FUN, ...)

Arguments

Details

https://stat.ethz.ch/pipermail/r-devel/2007-November/047318.html

Value

A new function partially determined

Examples

double <- Curry(`*`, e1=2)
stopifnot(double(4) == 8)

Lazy curry; thanks, Jamie! <https://github.com/klutometis/R-functional/issues/1>

Description

Lazy curry; thanks, Jamie! <https://github.com/klutometis/R-functional/issues/1>

Usage

CurryL(FUN, ...)

Arguments

Value

A new function that, when called, lazily evaluates FUN with the pre-specified and subsequent arguments.

Examples

# day is not defined; thanks, Jamie Folson.
CurryL(function(...) match.call(),
       x=5,
       y=as.Date(day))(z=as.Date(day,"%Y"))

Identity function.

Description

Is concatenation benign?

Usage

Identity(...)

Arguments

Value

The tautologized arguments, concatenated

Examples

list.copy <- function(list)
  Reduce(Identity, list)

list <- c(1, 2, 3)
stopifnot(list.copy(list) == list)

Negate a function; borrowed from src/library/base/R/funprog.R for pre-2.7 Rs.

Description

Negate a function; borrowed from src/library/base/R/funprog.R for pre-2.7 Rs.

Usage

Negate(f)

Arguments

Value

The negated function

Examples

is.even <- function(a) a%%2 == 0
is.odd <- Negate(is.even)
stopifnot(Reduce(`&&`, Map(is.odd, c(1, 3, 5))))

Thanks, Gabor; see <http://stackoverflow.com/a/23726989>: swaps the first two arguments in a function.

Description

Thanks, Gabor; see <http://stackoverflow.com/a/23726989>: swaps the first two arguments in a function.

Usage

Swap(f)

Arguments

Value

A function with swapped arguments

Composition with multiple arguments.

Description

Thanks, Alexander Davis!

Usage

multi.argument.Compose(...)

Arguments

Value

A composed function

Examples

f <- function(x, y) x+y
g <- function(x) x*2
stopifnot(multi.argument.Compose(f, g)(1,1) == 4)