1 files changed, 59 insertions, 0 deletions
diff --git a/src/compiler/scala/tools/nsc/interpreter/LoopCommands.scala b/src/compiler/scala/tools/nsc/interpreter/LoopCommands.scala
new file mode 100644
index 0000000000..24fde9425f
--- /dev/null
+++ b/src/compiler/scala/tools/nsc/interpreter/LoopCommands.scala
@@ -0,0 +1,59 @@
+/* NSC -- new Scala compiler
+ * Copyright 2005-2011 LAMP/EPFL
+ * @author  Paul Phillips
+ */
+
+package scala.tools.nsc
+package interpreter
+
+trait LoopCommands {
+  protected def out: java.io.PrintWriter
+
+  // a single interpreter command
+  sealed abstract class LoopCommand extends (List[String] => Result) {
+    def name: String
+    def help: String
+    def commandError(msg: String) = {
+      out.println(":" + name + " " + msg + ".")
+      Result(true, None)
+    }
+    def usage(): String
+  }
+  case class NoArgs(name: String, help: String, f: () => Result) extends LoopCommand {
+    def usage(): String = ":" + name
+    def apply(args: List[String]) = if (args.isEmpty) f() else commandError("accepts no arguments")
+  }
+
+  case class LineArg(name: String, help: String, f: (String) => Result) extends LoopCommand {
+    def usage(): String = ":" + name + " "
+    def apply(args: List[String]) = f(args mkString " ")
+  }
+
+  case class OneArg(name: String, help: String, f: (String) => Result) extends LoopCommand {
+    def usage(): String = ":" + name + " "
+    def apply(args: List[String]) =
+      if (args.size == 1) f(args.head)
+      else commandError("requires exactly one argument")
+  }
+
+  case class VarArgs(name: String, help: String, f: (List[String]) => Result) extends LoopCommand {
+    def usage(): String = ":" + name + " [arg]"
+    def apply(args: List[String]) = f(args)
+  }
+
+  // the result of a single command
+  case class Result(val keepRunning: Boolean, val lineToRecord: Option[String])
+  object Result {
+    // the default result means "keep running, and don't record that line"
+    val default = Result(true, None)
+
+    // most commands do not want to micromanage the Result, but they might want
+    // to print something to the console, so we accomodate Unit and String returns.
+    implicit def resultFromUnit(x: Unit): Result = default
+    implicit def resultFromString(msg: String): Result = {
+      out println msg
+      default
+    }
+  }
+}
+