diff --git a/FusionCalculator.csproj b/FusionCalculator.csproj
new file mode 100644
index 0000000..eddfd19
--- /dev/null
+++ b/FusionCalculator.csproj
@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <RollForward>LatestMajor</RollForward>
+    <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
+  </PropertyGroup>
+
+</Project>
\ No newline at end of file
diff --git a/build.sh b/build_c.sh
similarity index 100%
rename from build.sh
rename to build_c.sh
diff --git a/build_cs.sh b/build_cs.sh
new file mode 100644
index 0000000..b1bab72
--- /dev/null
+++ b/build_cs.sh
@@ -0,0 +1,21 @@
+#!/bin/bash
+set -eo pipefail
+
+rm -rf out bin
+mkdir out
+
+SRC_FILES="$(find src/ -name '*.fu')"
+INCLUDES=""
+for src_file in $SRC_FILES; do
+    INCLUDES="$INCLUDES -r $src_file"
+done
+for src_file in $SRC_FILES; do
+    echo "---------[$src_file]---------"
+    out_file="out/$(basename $src_file .fu).cs"
+    args="-l cs -D CS -n FusionCalculator $INCLUDES -o $out_file $src_file"
+    echo "fu $args"
+    fut $args
+done
+
+echo "---------[FusionCalculator.csproj]---------"
+dotnet build FusionCalculator.csproj  -o bin
diff --git a/src/Calculator.fu b/src/Calculator.fu
index da81c4d..f7b7b26 100644
--- a/src/Calculator.fu
+++ b/src/Calculator.fu
@@ -11,11 +11,11 @@ public static class Calculator
 
     public static double Calculate(string exprStr)
     {
-        Lexer() lexer = { ExprStr = exprStr};
-        List<Token()> tokens = lexer.Lex();
+        Lexer() lexer;
+        List<Token()> tokens = lexer.Lex(exprStr);
         // lexer.PrintTokens();
-        Parser() parser = { TokenStorage = tokens };
-        IExpression expr = parser.Parse();
+        Parser() parser;
+        IExpression expr = parser.Parse(tokens);
         // parser.PrintGraphVizCode();
         return expr.Calculate();
     }
diff --git a/src/Expressions/NumericalExpression.fu b/src/Expressions/NumericalExpression.fu
index 13268b7..1fbab91 100644
--- a/src/Expressions/NumericalExpression.fu
+++ b/src/Expressions/NumericalExpression.fu
@@ -1,5 +1,12 @@
 class NumericExpression : IExpression
 {
     double N;
+
+    internal void Init!(double n){
+        N = n;
+    }
+
+    internal NumericExpression(){ N=Math.NaN; }
+
     internal override double Calculate() => N;
 }
diff --git a/src/Lexer.fu b/src/Lexer.fu
index cb72d2e..dfc3257 100644
--- a/src/Lexer.fu
+++ b/src/Lexer.fu
@@ -30,14 +30,15 @@ class Lexer
     internal void PrintTokens(){
         for(int i = 0; i < TokenStorage.Count; i++){
             Token() tok = TokenStorage[i];
-            int tokType = tok.GetType();
+            int tokType = tok.GetTokType();
             string() tokStr = tok.GetStr();
             Console.WriteLine($"'{tokStr}' {tokType:D1}");
         }
     }
 
-    internal List<Token()> Lex!()
-    {
+    internal List<Token()> Lex!(string exprStr){
+        ExprStr = exprStr;
+
         while (i < ExprStr.Length)
         {
             switch (ExprStr[i])
diff --git a/src/Parser.fu b/src/Parser.fu
index 026dee0..1cb2907 100644
--- a/src/Parser.fu
+++ b/src/Parser.fu
@@ -6,11 +6,14 @@ class Parser
     Token() TokZero;
 
     internal Parser(){
-        RootExpression = new NumericExpression { N = Math.NaN };
+        NumericExpression# nan = new NumericExpression();
+        nan.Init(Math.NaN);
+        RootExpression = nan;
         TokZero = Token.Create("0", 0, 1, Token.Type_Number);
     }
 
-    internal IExpression# Parse!(){
+    internal IExpression# Parse!(List<Token()> tokens){
+        TokenStorage = tokens;
         SortTokensInRPN();
         BuildExpressionTree();
         return RootExpression;
@@ -29,7 +32,7 @@ class Parser
 
         for(int i = 0; i < TokenStorage.Count; i++){
             Token tok = TokenStorage[i];
-            int type = tok.GetType();
+            int type = tok.GetTokType();
 
             switch(type){
                 case Token.Type_Number:
@@ -43,7 +46,7 @@ class Parser
                 case Token.Type_OperatorSub:
                     if(type == Token.Type_OperatorSub && prevTokType == Token.Type_BracketOpen)
                         TokensInRPN.AddToEnd(TokZero);
-                    while(RPNStack.Count != 0 && RPNStack.Peek().GetType() >= type){
+                    while(RPNStack.Count != 0 && RPNStack.Peek().GetTokType() >= type){
                         Token op2 = RPNStack.Pop();
                         TokensInRPN.AddToEnd(op2);
                     }
@@ -55,16 +58,16 @@ class Parser
                 case Token.Type_BracketClose:
                     while(RPNStack.Count != 0){
                         Token op2 = RPNStack.Pop();
-                        if(op2.GetType() == Token.Type_BracketOpen)
+                        if(op2.GetTokType() == Token.Type_BracketOpen)
                             break;
                         TokensInRPN.AddToEnd(op2);
                     }
                     break;
                 case Token.Type_Literal:
-                    ThrowError("not implemented");
+                    ThrowError($"token '{tok.GetStr()}' isn't implemented");
                     break;
                 default:
-                    ThrowError("unexpected token type");
+                    ThrowError($"unexpected token type '{type}'");
                     break;
             }
 
@@ -85,11 +88,13 @@ class Parser
         TokenLinkedListNode? tokenNode = TokensInRPN.GetFirstNode();
         while(tokenNode != null){
             Token tok = tokenNode.GetValue();
-            int type = tok.GetType();
+            int type = tok.GetTokType();
 
             switch(type){
                 case Token.Type_Number:
-                    expressionStack.Push(new NumericExpression { N = StringToDouble(tok.GetStr()) });
+                    NumericExpression# num = new NumericExpression();
+                    num.Init(StringToDouble(tok.GetStr()));
+                    expressionStack.Push(num);
                     break;
                 case Token.Type_OperatorPow:
                     PushOperatorExpression(expressionStack, tok, new OperatorExpressionPow());
@@ -110,16 +115,16 @@ class Parser
                     PushOperatorExpression(expressionStack, tok, new OperatorExpressionSub());
                     break;
                 case Token.Type_BracketClose:
-                    ThrowError("unexpected (");
+                    ThrowError("unexpected '('");
                     break;
                 case Token.Type_BracketOpen:
-                    ThrowError("unexpected )");
+                    ThrowError("unexpected ')'");
                     break;
                 case Token.Type_Literal:
-                    ThrowError("not implemented");
+                    ThrowError($"token '{tok.GetStr()}' isn't implemented");
                     break;
                 default:
-                    ThrowError($"unexpected token type: {type}");
+                    ThrowError($"unexpected token type '{type}'");
                     break;
             }
 
@@ -151,7 +156,7 @@ class Parser
 
     void PushOperatorExpression(Stack<IExpression#>! expressionStack, Token tok, OperatorExpression# opExpr) {
         if(expressionStack.Count < 2){
-            ThrowError($"unexpected operator: {tok.GetStr()}");
+            ThrowError($"unexpected operator '{tok.GetStr()}'");
             return;
         }
         IExpression b = expressionStack.Pop();
diff --git a/src/Token.fu b/src/Token.fu
index 8216a09..7db58f3 100644
--- a/src/Token.fu
+++ b/src/Token.fu
@@ -29,5 +29,5 @@ class Token
     }
 
     internal string() GetStr() => Str.Substring(StartIndex, Length);
-    internal int GetType() => Type;
+    internal int GetTokType() => Type;
 }
diff --git a/src/TokenLinkedList.fu b/src/TokenLinkedList.fu
index aff255f..f5790e7 100644
--- a/src/TokenLinkedList.fu
+++ b/src/TokenLinkedList.fu
@@ -35,12 +35,11 @@ class TokenLinkedList {
     }
 
     internal TokenLinkedListNode# CreateOrphanedNode!(Token tok) {
-        TokenLinkedListNode# sharedPtr = new TokenLinkedListNode { 
-            Value = tok, 
-            Prev = null, 
-            Next = null 
-        };
-        return sharedPtr;
+        TokenLinkedListNode# node = new TokenLinkedListNode();
+        node.SetValue(tok);
+        node.SetPrev(null); 
+        node.SetNext(null);
+        return node;
     }
 
     // Can be used by GraphViz to create node graph.
diff --git a/src/TokenLinkedListNode.fu b/src/TokenLinkedListNode.fu
index 359d2b8..e7d2520 100644
--- a/src/TokenLinkedListNode.fu
+++ b/src/TokenLinkedListNode.fu
@@ -7,10 +7,10 @@ class TokenLinkedListNode {
     internal void SetValue!(Token value) { Value = value; }
 
     internal TokenLinkedListNode!? GetPrev() => Prev;
-    internal void SetPrev!(TokenLinkedListNode! prev) { Prev = prev; }
+    internal void SetPrev!(TokenLinkedListNode!? prev) { Prev = prev; }
 
     internal TokenLinkedListNode!? GetNext() => Next;
-    internal void SetNext!(TokenLinkedListNode! next) { Next = next; }
+    internal void SetNext!(TokenLinkedListNode!? next) { Next = next; }
 
     internal void InsertAfter!(TokenLinkedListNode! prev){
         Next = prev.GetNext();