Make CASCRepl accessible from main progress

src/CASC-Compiler/Program.cs

@@ -18,10 +18,20 @@ private static void Main(string[] args)
         {
             if (args.Length == 0)
             {
-                Console.Error.WriteLine("Usage: casc <source-path>");
+                Console.Error.WriteLine(
+                "Usage: casc <source-directory-path>\n   or  casc repl\nIf you are running CASC by local executable file,\nconsider adds arguments behind the excutable file."
+                );
                 return;
             }
 
+            if (string.Equals(args[0], "repl"))
+            {
+                var repl = new CASCRepl();
+                repl.Run();
+                return;
+            }
+
+
             var paths = GetFilePaths(args);
             var syntaxTrees = new List<SyntaxTree>();
             var hasError = false;

src/CASC-Console/CASCRepl.cs

@@ -3,13 +3,12 @@
 using System.Collections.Generic;
 using System.Linq;
 using System;
-using CASC.CodeParser.Text;
 using CASC.CodeParser.Symbols;
 using CASC.IO;
 
 namespace CASC
 {
-    internal sealed class CASCRepl : Repl
+    public sealed class CASCRepl : Repl
     {
         private Compilation _previous;
         private bool _showTree;

src/CASC-Console/Repl.cs

@@ -5,7 +5,7 @@
 
 namespace CASC
 {
-    internal abstract class Repl
+    public abstract class Repl
     {
         private List<string> _submissionHistory = new List<string>();
         private int _submissionHistoryIndex;