From 455be9eab47fbcbb74d687d6c177c042a37f7c97 Mon Sep 17 00:00:00 2001
From: Nicolas Zabel <nicolas.zabel@evhr.net>
Date: Fri, 18 Apr 2014 15:41:14 +0200
Subject: [PATCH 1/2] completed assignment

---
 cachematrix.R | 33 ++++++++++++++++++++++++++-------
 1 file changed, 26 insertions(+), 7 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index a50be65aa44..b2a186c2154 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -1,15 +1,34 @@
-## Put comments here that give an overall description of what your
-## functions do
+## Cache the result of solve in an internal structure along with the matrix
 
-## Write a short comment describing this function
 
-makeCacheMatrix <- function(x = matrix()) {
+## makeCacheMatrix is a closure that defines the accessors 
+## and the mutators of a matrix (x) and its inverse (i)
 
+makeCacheMatrix <- function(x = matrix()) {
+  i <- NULL	# inverse of the matrix (cache)
+  set <- function(y) {
+    x <<- y		# assign the new matrix y to x, the internal store of the matrix
+    i <<- NULL 	# invalidate the cached inverse of the matrix x
+  }
+  get <- function() x		# return the value of the matrix x
+  setSolved <- function(j) i <<- j # cache the inverse of the matrix x
+  getSolved <- function() i # return the value of the inverse
+  list(get = get, set = set, getSolved = getSolved, setSolved = setSolved)
 }
 
 
-## Write a short comment describing this function
+## Cache the result of solve (ie the inverse of x) into its internal variable i
 
 cacheSolve <- function(x, ...) {
-        ## Return a matrix that is the inverse of 'x'
-}
+  ## Return a matrix that is the inverse of 'x'
+  i <- x$getSolved()	# retrieve the cached inverse
+  if (!is.null(i)) {
+    # the cached inverse has not been invalidated by an update (x$set) of the matrix
+    message("getting cached data")
+    return (i)
+  }
+  m <- x$get()	# retrieve the data of the matrix
+  i <- solve(m,...)
+  x$setSolved(i)
+  i
+}
\ No newline at end of file

From 2a0cae93379b4d27ab2a196980877b92a3713141 Mon Sep 17 00:00:00 2001
From: Nicolas Zabel <nicolas.zabel@evhr.net>
Date: Fri, 18 Apr 2014 15:48:29 +0200
Subject: [PATCH 2/2] more comments

---
 cachematrix.R | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/cachematrix.R b/cachematrix.R
index b2a186c2154..5380dacfabe 100644
--- a/cachematrix.R
+++ b/cachematrix.R
@@ -28,7 +28,7 @@ cacheSolve <- function(x, ...) {
     return (i)
   }
   m <- x$get()	# retrieve the data of the matrix
-  i <- solve(m,...)
-  x$setSolved(i)
-  i
-}
\ No newline at end of file
+  i <- solve(m,...) # compute the inverse
+  x$setSolved(i) # cache the inverse
+  i # return the inverse
+}