Compile function once, during the registration.

Author: yallie

README.md

@@ -1,6 +1,9 @@
 Sprache.Calc
 ============
 
+[![Appveyor build status](https://ci.appveyor.com/api/projects/status/qswh0wj2uv3w502v?svg=true)](https://ci.appveyor.com/project/yallie/sprache-calc)
+[![Tests](https://img.shields.io/appveyor/tests/yallie/sprache-calc.svg)](https://ci.appveyor.com/project/yallie/sprache-calc/build/tests)
+
 This library provides easy to use extensible expression evaluator based on [LinqyCalculator sample](https://github.com/sprache/Sprache/blob/master/samples/LinqyCalculator/ExpressionParser.cs).
 The evaluator supports arithmetic operations, custom functions and parameters. It takes string
 representation of an expression and converts it to a structured LINQ expression instance

Sprache.Calc.Tests/XtensibleCalculatorFacts.cs

@@ -32,12 +32,9 @@ protected override object[] LambdaArguments
 		public void UserFunctionCanWork()
 		{
 			var calc = (XtensibleCalculator) CreateCalculator();
-			
 			calc.RegisterFunction("User", (aU,bU,cU) => calc.ParseExpression("Min(a,b,c)", new Dictionary<string,double>(){{"a",aU},{"b",bU},{"c",cU}}).Compile().Invoke());
 
-		
 			var func = calc.ParseExpression("User(a,b,c)", new Dictionary<string,double>(){{"a",1},{"b",2},{"c",3}}).Compile();
-			
 			Assert.Equal(1, func());
 		}
 
@@ -48,7 +45,7 @@ public void StringUserFunctionCanWork()
 			calc.RegisterFunction("UserB", "Min(a,b,c)", "a", "b", "c");
 			var func = calc.ParseExpression("UserB(a,b,c)",
 				new Dictionary<string, double>() {{"a", 1}, {"b", 2}, {"c", 3}}).Compile();
-			
+
 			Assert.Equal(1, func());
 		}
 

Sprache.Calc/Sprache.Calc.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netstandard1.6</TargetFramework>
+    <TargetFrameworks>netstandard1.6;netstandard2.0</TargetFrameworks>
     <PackageVersion></PackageVersion>
     <Title>Sprache Calculator</Title>
     <Authors>Alexey Yakovlev, Andrey Leskov</Authors>
@@ -13,11 +13,14 @@
     <RepositoryUrl>https://github.com/yallie/Sprache.Calc</RepositoryUrl>
     <RepositoryType>git</RepositoryType>
     <PackageTags>sprache expression expressions evaluator calculator parser parsers linq monad</PackageTags>
-    <PackageReleaseNotes>Sprache toolkit grammar inheritance sample. Updated for .Net Standart 1.6 and added functionality to add user-defined functions from strings. For more details, see https://github.com/yallie/Sprache.Calc</PackageReleaseNotes>
+    <PackageReleaseNotes>Sprache toolkit grammar inheritance sample. Updated for .Net Standard 1.6 and added functionality to add user-defined functions from strings. For more details, see https://github.com/yallie/Sprache.Calc</PackageReleaseNotes>
   </PropertyGroup>
 
   <ItemGroup>
     <PackageReference Include="Sprache" Version="2.2.0" />
+  </ItemGroup>
+
+  <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard1.6' ">
     <PackageReference Include="System.Reflection.TypeExtensions" Version="4.5.1" />
   </ItemGroup>
 

Sprache.Calc/XtensibleCalculator.cs

@@ -151,18 +151,25 @@ public XtensibleCalculator RegisterFunction(string name, Func<double, double, do
 			CustomFuctions[MangleName(name, 5)] = x => function(x[0], x[1], x[2], x[3], x[4]);
 			return this;
 		}
-		
+
 		public XtensibleCalculator RegisterFunction(string name, string functionExpression, params string[] parameters)
 		{
+			// Func<Dictionary, double>
+			var compiledFunction = ParseFunction(functionExpression).Compile();
+
 			//syntactic sugar: ParseExpression("a + b / c", "a","b","c")
 			CustomFuctions[MangleName(name, parameters.Length)] = x =>
 			{
-				var parametersDictionary = new Dictionary<string,double>();
-				for(int paramSeq = 0;paramSeq < parameters.Length; paramSeq++)
-					parametersDictionary.Add(parameters[paramSeq],x[paramSeq]);
-
-				return this.ParseExpression(functionExpression,parametersDictionary).Compile().Invoke();
+				// convert double[] to Dictionary
+				var parametersDictionary = new Dictionary<string, double>();
+				for (int paramSeq = 0; paramSeq < parameters.Length; paramSeq++)
+				{
+					parametersDictionary.Add(parameters[paramSeq], x[paramSeq]);
+				}
+
+				return compiledFunction(parametersDictionary);
 			};
+
 			return this;
 		}
 	}