Eval parser

NadekoBot/Modules/Searches/Commands/EvalCommand.cs

@@ -0,0 +1,88 @@
+using NadekoBot.Classes;
+using System;
+using Mathos.Parser;
+using System.Threading.Tasks;
+using Discord.Commands;
+using System.Text.RegularExpressions;
+
+namespace NadekoBot.Modules.Searches.Commands
+{
+    class EvalCommand : DiscordCommand
+    {
+        public EvalCommand(DiscordModule module) : base(module)
+        {
+        }
+
+        internal override void Init(CommandGroupBuilder cgb)
+        {
+            cgb.CreateCommand(Module.Prefix + "evaluate")
+                .Alias(Module.Prefix + "eval")
+                .Description("Evaluate a mathematical expression")
+                .Parameter("expression", ParameterType.Unparsed)
+                .Do(EvalFunc());
+        }
+
+
+        private CustomParser parser = new CustomParser();
+        private Func<CommandEventArgs, Task> EvalFunc() => async e =>
+        {
+            string expression = e.GetArg("expression")?.Trim();
+            if (string.IsNullOrWhiteSpace(expression))
+            {
+                await e.Channel.SendMessage("Must give expression");
+                return;
+            }
+            string answer = evaluate(expression);
+            if (answer == null)
+            {
+                await e.Channel.SendMessage($"Expression {expression} failed to evaluate");
+                return;
+            }
+            await e.Channel.SendMessage($"`result: {answer}`");
+        };
+
+        private string evaluate(string expression)
+        {
+            //check for factorial
+            expression = Regex.Replace(expression, @"\d+!", x => x.Value + "0");
+            try
+            {
+                string result = parser.Parse(expression).ToString();
+                return result;
+            }
+            catch (OverflowException e)
+            {
+                return $"Overflow error on {expression}";
+            }
+            catch (FormatException e)
+            {
+                return $"\"{expression}\" was not formatted correctly";
+            }
+        }
+
+        
+
+        class CustomParser : MathParser
+        {
+            public CustomParser() : base()
+            {
+                OperatorList.Add("!");
+                OperatorList.Add("_");
+                OperatorAction.Add("!", (x, y) => factorial(x));
+                OperatorAction.Add("_", (x, y) => 10.130M);
+            }
+
+            static decimal factorial(decimal x)
+            {
+                decimal y = x-1;
+                while (y >0)
+                {
+                    x = x * y--;
+                }
+                return x;
+            }
+        }
+
+
+    }
+}

NadekoBot/Modules/Searches/SearchesModule.cs

@@ -28,6 +28,7 @@ namespace NadekoBot.Modules.Searches
             commands.Add(new ConverterCommand(this));
             commands.Add(new RedditCommand(this));
 			commands.Add(new WowJokeCommand(this));
+            commands.Add(new EvalCommand(this));
             rng = new Random();
         }
 

NadekoBot/NadekoBot.csproj

@@ -89,6 +89,10 @@
       <HintPath>..\packages\Manatee.Trello.WebApi.1.0.1\lib\net45\Manatee.Trello.WebApi.dll</HintPath>
       <Private>True</Private>
     </Reference>
+    <Reference Include="MathParser, Version=1.0.10.1, Culture=neutral, processorArchitecture=MSIL">
+      <SpecificVersion>False</SpecificVersion>
+      <HintPath>lib\MathParser.dll</HintPath>
+    </Reference>
     <Reference Include="Newtonsoft.Json, Version=8.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed, processorArchitecture=MSIL">
       <HintPath>..\packages\Newtonsoft.Json.8.0.3\lib\net45\Newtonsoft.Json.dll</HintPath>
       <Private>True</Private>
@@ -128,6 +132,7 @@
     <Compile Include="Modules\CustomReactions\CustomReactions.cs" />
     <Compile Include="Modules\Programming\Commands\HaskellRepl.cs" />
     <Compile Include="Modules\Programming\ProgrammingModule.cs" />
+    <Compile Include="Modules\Searches\Commands\EvalCommand.cs" />
     <Compile Include="Modules\Searches\Commands\IMDB\ImdbMovie.cs" />
     <Compile Include="Modules\Searches\Commands\IMDB\ImdbScraper.cs" />
     <Compile Include="Classes\IncidentsHandler.cs" />
@@ -475,6 +480,7 @@
     </ProjectReference>
   </ItemGroup>
   <ItemGroup>
+    <Content Include="lib\MathParser.dll" />
     <Content Include="lib\ScaredFingers.UnitsConversion.dll" />
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />