add piston nix pkg for scala

runtimes/default.nix

@@ -60,4 +60,5 @@ args: {
     "fpc-pascal" = import ./fpc-pascal.nix args;
     "brainfuck" = import ./brainfuck.nix args;
     "node-coffeescript" = import ./node-coffeescript.nix args;
+    "jvm-scala" = import ./jvm-scala.nix args;
 }

runtimes/jvm-scala.nix

@@ -0,0 +1,54 @@
+{pkgs, piston, ...}:
+let
+    pkg = pkgs.scala;
+    java = pkgs.jdk8;
+    sed = pkgs.gnused;
+in piston.mkRuntime {
+    language = "scala";
+    version = pkg.version;
+    runtime = "jvm";
+
+    aliases = [
+        "sc"
+    ];
+
+    compile = ''
+        # Compile scala classes into a jar file
+        ${pkg}/bin/scalac "$@" -d out.jar
+
+        # Capture extra class-path libraries
+        java_libs="$(echo ${java}/lib/openjdk/lib/*.jar | ${sed}/bin/sed 's/\s/\\n  /g')"
+        scala_libs="$(echo ${pkg}/lib/*.jar | ${sed}/bin/sed 's/\s/\\n  /g')"
+
+        echo -e "Class-Path:  $java_libs
+          $scala_libs
+        " > classPath
+
+        # Update the jar manifest with scala libs
+        ${java}/bin/jar umf classPath out.jar
+    '';
+
+    run = ''
+        # Run jar from compile
+        shift
+        ${java}/bin/java -jar out.jar "$@"
+    '';
+
+    tests = [
+        (piston.mkTest {
+            files = {
+                "test.sc" = ''
+                    object Main {
+                        def main(args: Array[String]) = {
+                            println("OK")
+                        }
+                    }
+                '';
+            };
+            args = [];
+            stdin = "";
+            packages = [];
+            main = "test.sc";
+        })
+    ];
+}