[Ubuntu] Install 3 latest Haskell version and latest Cabal version (#939)

* Remove deprecated versions

* add regexp for the latest versions

* refactor some checks

* change cabal version

* change version retrieval to awk

* minor comments improvment

images/linux/scripts/installers/haskell.sh

@@ -6,7 +6,6 @@
 
 # Source the helpers for use with the script
 source $HELPER_SCRIPTS/document.sh
-source $HELPER_SCRIPTS/os.sh
 
 # Install Herbert V. Riedel's PPA for managing multiple version of ghc on ubuntu.
 # https://launchpad.net/~hvr/+archive/ubuntu/ghc
@@ -14,25 +13,15 @@ apt-get install -y software-properties-common
 add-apt-repository -y ppa:hvr/ghc
 apt-get update
 
-# Install various versions of ghc and cabal
-if isUbuntu20 ; then
-    ghcVersions="8.6.5 8.8.3 8.10.1"
-    cabalVersions="3.2"
-fi
-
-if isUbuntu16 || isUbuntu18 ; then
-    # Install various versions of ghc and cabal
-    ghcVersions="8.0.2 8.2.2 8.4.4 8.6.2 8.6.3 8.6.4 8.6.5 8.8.1 8.8.2 8.8.3 8.10.1"
-    cabalVersions="2.0 2.2 2.4 3.0 3.2"
-fi
+# Get 3 latest Haskell versions and latest Cabal version
+ghcVersions=$(apt-cache search "^ghc-" | grep -Po '(\d*\.){2}\d*' | awk 'BEGIN {FS=OFS=SUBSEP="."}{if (arr[$1,$2] < $3) arr[$1,$2] = $3} END {for (i in arr) print i,arr[i]}' | sort --version-sort | tail -3)
+cabalVersion=$(apt-cache search cabal-install-[0-9] | grep -Po '\d*\.\d*' | sort --unique --version-sort | tail -1)
 
 for version in $ghcVersions; do
     apt-get install -y ghc-$version
 done
 
-for version in $cabalVersions; do
-    apt-get install -y cabal-install-$version
-done
+apt-get install -y cabal-install-$cabalVersion
 
 # Install the latest stable release of haskell stack
 curl -sSL https://get.haskellstack.org/ | sh
@@ -46,13 +35,13 @@ for version in $ghcVersions; do
         exit 1
     fi
 done
-# Check all cabal versions
-for version in $cabalVersions; do
-    if ! command -v /opt/cabal/$version/bin/cabal; then
-        echo "cabal $version was not installed"
-        exit 1
-    fi
-done
+
+# Check cabal
+if ! command -v /opt/cabal/$cabalVersion/bin/cabal; then
+    echo "cabal $cabalVersion was not installed"
+    exit 1
+fi
+
 # Check stack
 if ! command -v stack; then
     exit 1
@@ -60,9 +49,7 @@ fi
 
 # Document what was added to the image
 echo "Lastly, documenting what we added to the metadata file"
-for version in $cabalVersions; do
-    DocumentInstalledItem "Haskell Cabal ($(/opt/cabal/$version/bin/cabal --version))"
-done
+DocumentInstalledItem "Haskell Cabal ($(/opt/cabal/$cabalVersion/bin/cabal --version))"
 for version in $ghcVersions; do
     DocumentInstalledItem "GHC ($(/opt/ghc/$version/bin/ghc --version))"
 done