cleaner matching & output for roll command

Command.cs

@@ -5,13 +5,19 @@ namespace Dungeoneer {
 	public sealed class Command {
 
 		public static void Roll(IList<string> args) {
+			//	don't do anything with empty expressions
 			if(args.Count == 0)
 				return;
 			var expression = "";
 
+			var diePattern = new Regex(@"\d+d\d+");
+
+			//	reassemble split args and substitute die notation
 			foreach(string arg in args) {
 				string part;
-				if(arg.Contains('d')) {
+
+				var dieCheck = diePattern.Match(arg);
+				if(dieCheck.Success) {
 					var parts = arg.Split('d');
 					var first = parts[0];
 					var second = parts[1];
@@ -26,19 +32,34 @@ namespace Dungeoneer {
 						return;
 					}
 
-					var result = 0;
+					var rolls = "( ";
-					for(int i = 0; i < count; i++)
+					for(int i = 0; i < count; i++) {
-						result += Util.Roll(sides);
+						string result;
-					part = result.ToString();
+						var roll = Util.Roll(sides);
+						if(i < count - 1)
+							result = $"{roll} + ";
+						else
+							result = $"{roll} ";
+						rolls += result;
+					}
+					rolls += ")";
+					part = rolls;
 				} else
 					part = arg;
 				expression += $"{part} ";
 			}
 
-			dynamic output = Scripting.Expr($"eval('{expression}')");
+			dynamic output;
+			try { output = Scripting.Expr($"eval('{expression}')"); }
+			catch {
+				Console.WriteLine("invalid expression");
+				return;
+			}
 			Console.WriteLine($"{expression}\n=> {output}");
 		}
 
+
+
 	}
 
 }