r-lib · jimhester · Jan 22, 2016 · Mar 19, 2015
diff --git a/NAMESPACE b/NAMESPACE
@@ -1,6 +1,7 @@
 # Generated by roxygen2 (4.0.0): do not edit by hand
 
 export(forget)
+export(has.cache)
 export(is.memoised)
 export(is.memoized)
 export(memoise)

diff --git a/R/memoise.r b/R/memoise.r
@@ -138,3 +138,24 @@ forget <- function(f) {
 is.memoised <- is.memoized <- function(f) {
   identical(attr(f, "memoised"), TRUE)
 }
+
+#' Test whether a memoised function has been cached for particular arguments.
+#' @param f Function to test.
+#' @param ... arguments to function.
+#' @seealso \code{\link{is.memoised}}, \code{\link{memoise}}
+#' @export has.cache
+#' @examples
+#' mem_sum <- memoise(sum)
+#' has.cache( mem_sum, 1, 2, 3) # FALSE
+#' mem_sum(1, 2, 3)
+#' has.cache( mem_sum, 1, 2, 3) # TRUE
+has.cache <- function(f, ...) {
+  if(!is.memoised(f)) return(FALSE)
+
+  hash <- digest(list(...))
+  env <- environment(f)
+  if (!exists("cache", env, inherits = FALSE)) return(FALSE)
+  cache <- get("cache", env)
+
+  cache$has_key(hash)
+}
diff --git a/man/has.cache.Rd b/man/has.cache.Rd
@@ -0,0 +1,26 @@
+% Generated by roxygen2 (4.1.0): do not edit by hand
+% Please edit documentation in R/memoise.r
+\name{has.cache}
+\alias{has.cache}
+\title{Test whether a memoised function has been cached for particular arguments.}
+\usage{
+has.cache(f, ...)
+}
+\arguments{
+\item{f}{Function to test.}
+
+\item{...}{arguments to function.}
+}
+\description{
+Test whether a memoised function has been cached for particular arguments.
+}
+\examples{
+mem_sum <- memoise(sum)
+has.cache( mem_sum, 1, 2, 3) # FALSE
+mem_sum(1, 2, 3)
+has.cache( mem_sum, 1, 2, 3) # TRUE
+}
+\seealso{
+\code{\link{is.memoised}}, \code{\link{memoise}}
+}
+