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[m17n/m17n-lib-cs.git] / MSymbol.cs

diff --git a/MSymbol.cs b/MSymbol.cs
index 5bfc64a..b92bcbf 100644 (file)
--- a/MSymbol.cs
+++ b/MSymbol.cs
@@ -22,8 +22,12 @@ namespace M17N.Core
 
     private MSymbolData data;
 
-    static public MSymbol nil = new MSymbol ("nil");
-    static public MSymbol t = new MSymbol ("t");
+    public static MSymbol nil = new MSymbol ("nil");
+    public static MSymbol t = new MSymbol ("t");
+    public static MSymbol symbol = new MSymbol ("symbol");
+    public static MSymbol mtext = new MSymbol ("mtext");
+    public static MSymbol plist = new MSymbol ("plist");
+    public static MSymbol integer = new MSymbol ("integer");
 
     public MSymbol (string name)
     {
@@ -51,6 +55,8 @@ namespace M17N.Core
 
     public override bool Equals (object sym)
     {
+      if (sym == null)
+       return false;
       return (this.data == ((MSymbol) sym).data);
     }