From d3dd47ddf5fbda3841ed611245d98cb1da680821 Mon Sep 17 00:00:00 2001
From: Michael Sumner <mdsumner@gmail.com>
Date: Wed, 31 Jul 2019 02:02:58 +1000
Subject: [PATCH] doc for avoid build-time dependency #76 (#91)

* doc for avoid build-time dependency #76

* document() for Rd

* use preformatted

* No code with preformatted block
---
 R/memoise.R    | 16 ++++++++++++++++
 man/memoise.Rd | 16 ++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/R/memoise.R b/R/memoise.R
index 48915d5..1f24fe0 100644
--- a/R/memoise.R
+++ b/R/memoise.R
@@ -32,6 +32,22 @@
 #'     repeated.
 #' }
 #'
+#' It is recommended that functions in a package are not memoised at build-time,
+#' but when the package is loaded. The simplest way to do this is within
+#' \code{.onLoad()} with, for example
+#'
+#'
+#' \preformatted{
+#' # file.R
+#' fun <- function() {
+#'  some_expensive_process()
+#' }
+#'
+#' # zzz.R
+#' .onLoad <- function(pkgname, libname) {
+#'  fun <<- memoise::memoise(fun)
+#' }
+#' }
 #' @name memoise
 #' @title Memoise a function.
 #' @param f     Function of which to create a memoised copy.
diff --git a/man/memoise.Rd b/man/memoise.Rd
index c4fdfe1..fbdce05 100644
--- a/man/memoise.Rd
+++ b/man/memoise.Rd
@@ -52,6 +52,22 @@ Two example situations where \code{memoise} could be of use:
     once at the R prompt, or put it somewhere else where it won't get
     repeated.
 }
+
+It is recommended that functions in a package are not memoised at build-time,
+but when the package is loaded. The simplest way to do this is within
+\code{.onLoad()} with, for example
+
+\preformatted{
+# file.R
+fun <- function() {
+ some_expensive_process()
+}
+
+# zzz.R
+.onLoad <- function(pkgname, libname) {
+ fun <<- memoise::memoise(fun)
+}
+}
 }
 \examples{
 # a() is evaluated anew each time. memA() is only re-evaluated