make nan, +/-inf at runtime, avoid compiler errors

Fix issue #93
Add simple test (that also functions as a warning to devs) in Demo.cs

Author: molsonkiko

Demo Plugin/NppManagedPluginDemo/Demo.cs

@@ -136,6 +136,8 @@ static internal void CommandMenuInit()
             PluginBase.SetCommand(16, "---", null);
 
             PluginBase.SetCommand(17, "Print Scroll and Row Information", PrintScrollInformation);
+            
+            PluginBase.SetCommand(18, "Use NanInf class for -inf, inf, nan!!", PrintNanInf);
         }
 
         /// <summary>
@@ -443,6 +445,21 @@ static void DockableDlgDemo()
             }
             frmGoToLine.textBox1.Focus();
         }
+
+        static void PrintNanInf()
+        {
+            bool neginf_correct = double.IsNegativeInfinity(NanInf.neginf);
+            bool inf_correct = double.IsPositiveInfinity(NanInf.inf);
+            bool nan_correct = double.IsNaN(NanInf.nan);
+            string naninf = $@"-infinity == NanInf.neginf: {neginf_correct}
+infinity == NanInf.inf: {inf_correct}
+NaN == NanInf.nan: {nan_correct}
+If you want these constants in your plugin, you can find them in the NanInf class in PluginInfrastructure.
+DO NOT USE double.PositiveInfinity, double.NegativeInfinity, or double.NaN.
+You will get a compiler error if you do.";
+            notepad.FileNew();
+            editor.AppendTextAndMoveCursor(naninf);
+        }
         #endregion
     }
 }   

Demo Plugin/NppManagedPluginDemo/NppManagedPluginDemo.csproj

@@ -114,6 +114,9 @@
     <Compile Include="..\..\Visual Studio Project Template C#\PluginInfrastructure\UnmanagedExports.cs">
       <Link>PluginInfrastructure\UnmanagedExports.cs</Link>
     </Compile>
+    <Compile Include="..\..\Visual Studio Project Template C#\PluginInfrastructure\NanInf.cs">
+      <Link>PluginInfrastructure\NanInf.cs</Link>
+    </Compile>
     <Compile Include="Forms\frmGoToLine.cs">
       <SubType>Form</SubType>
     </Compile>

Visual Studio Project Template C#/PluginInfrastructure/NanInf.cs

@@ -0,0 +1,28 @@
+namespace Kbg.NppPluginNET.PluginInfrastructure
+{
+    /// <summary>
+    /// holds NaN, Infinity, and -Infinity as things generated at runtime<br></br>
+    /// because the compiler freaks out if it sees any of<br></br>
+    /// double.NegativeInfinity, double.PositiveInfinity, or double.NaN<br></br>
+    /// or any statically analyzed function of two constants that makes one of those constants<br></br>
+    /// like 1d/0d, 0d/0d, or -1d/0d.
+    /// </summary>
+    public class NanInf
+    {
+        /// <summary>
+        /// a/b<br></br>
+        /// may be necessary to generate infinity or nan at runtime
+        /// to avoid the compiler pre-computing things<br></br>
+        /// since if the compiler sees literal 1d/0d in the code
+        /// it just pre-computes it at compile time
+        /// </summary>
+        /// <param name="a"></param>
+        /// <param name="b"></param>
+        /// <returns></returns>
+        public static double Divide(double a, double b) { return a / b; }
+
+        public static readonly double inf = Divide(1d, 0d);
+        public static readonly double neginf = Divide(-1d, 0d);
+        public static readonly double nan = Divide(0d, 0d);
+    }
+}