src/library/base/man/forceAndCall.Rd

% File src/library/base/man/forceAndCall.Rd
% Part of the R package, https://www.R-project.org
% Copyright 1995-2015 R Core Team
% Distributed under GPL 2 or later

\name{forceAndCall}
\alias{forceAndCall}
\title{Call a function with Some Arguments Forced}
\description{
  Call a function with a specified number of leading arguments forced
  before the call if the function is a closure.
}
\usage{
forceAndCall(n, FUN, ...)
}
\arguments{
  \item{n}{number of leading arguments to force.}
  \item{FUN}{function to call.}
  \item{\dots}{arguments to \code{FUN}.}
}
\details{
  \code{forceAndCall} calls the function \code{FUN} with arguments
  specified in \code{\dots}.  If the value of \code{FUN} is a closure
  then the first \code{n} arguments to the function are evaluated
  (i.e. their delayed evaluation promises are forced) before executing
  the function body.  If the value of \code{FUN} is a primitive then
  the call \code{FUN(\dots)} is evaluated in the usual way.

  \code{forceAndCall} is intended to help defining higher order
  functions like \code{\link{apply}} to behave more reasonably when the
  result returned by the function applied is a closure that captured its
  arguments.
}
\seealso{
  \code{\link{force}}, \code{\link{promise}}, \code{\link{closure}}.
}
\keyword{programming}