Merge pull request #473 from sumitsahrawat/docker

Allow using pre-installed ipython

ubuntu-install.sh

@@ -3,33 +3,35 @@
 # Installation for Linux (tested on Ubuntu 14.10) from IHaskell repo directory.
 # TODO Split out setup for installation from Hackage released versions.
 
-ghc --version >& /dev/null
-if [ $? ]; then
-    true
-else
+if [ -z "$(which ghc)" ]; then
     echo "Please install ghc."
+    exit 1
 fi
 
-cabal --version >& /dev/null
-if [ $? ]; then
-    true
-else
+if [ -z "$(which cabal)" ]; then
     echo "Please install Cabal."
+    exit 1
 fi
 
-# Install IPython.
-# python-pip is out of date, causes problems, so we get the latest version
-# using easy_install instead.
-#sudo apt-get install python-pip
-sudo apt-get install -y python-dev
+# If ipython is installed, and has a major version >= 3, then use the
+# installed version. Otherwise we install from scratch.
+if [ -n "$(which ipython)" ] && { [ $(ipython --version | tr '.' ' ' | cut -f 1 -d ' ') -ge 3 ]; } then
+    echo "Using ipython already installed:" "$(which ipython)"
+else
+    # Install IPython.
+    # python-pip is out of date, causes problems, so we get the latest version
+    # using easy_install instead.
+    #sudo apt-get install python-pip
+    sudo apt-get install -y python-dev
 
-# To get easy_install
-sudo apt-get install -y python-setuptools
+    # To get easy_install
+    sudo apt-get install -y python-setuptools
 
-sudo easy_install -U pip
+    sudo easy_install -U pip
 
-# -H to use .cache in /root
-sudo -H pip install -U 'ipython[all]'
+    # -H to use .cache in /root
+    sudo -H pip install -U 'ipython[all]'
+fi
 
 # Make sure to have basic tools installed.
 cabal update