diff --git a/.gitignore b/.gitignore
index ea8c4bf..c2816a4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,3 @@
 /target
+
+log*
\ No newline at end of file
diff --git a/src/ll_grammar.rs b/src/ll_grammar.rs
index 819607f..e6569f5 100644
--- a/src/ll_grammar.rs
+++ b/src/ll_grammar.rs
@@ -436,6 +436,12 @@ impl<
 
 //
 
+pub trait Skippable {
+    fn skippable(&self) -> bool {
+        false
+    }
+}
+
 #[derive(Debug, Clone)]
 pub enum NodeChild<N, S> {
     Child(ParseTree<N, S>),
@@ -457,3 +463,41 @@ impl<N, S> ParseTree<N, S> {
         }
     }
 }
+
+impl<N: Skippable + Debug, S: Debug> ParseTree<N, S> {
+    /// cleanup the parse tree
+    /// does not work on a subtree
+    pub fn clean(self) -> Self {
+        self.clean_internal()
+            .expect("Clean only works on the main tree.")
+    }
+
+    /// internal clean
+    /// main node must not have a rule.
+    fn clean_internal(self) -> Result<Self, Vec<NodeChild<N, S>>> {
+        let childs = self
+            .childs
+            .into_iter()
+            .flat_map(|elem| match elem {
+                NodeChild::Child(parse_tree) => match parse_tree.clean_internal() {
+                    Ok(tree) => [NodeChild::Child(tree)].into(),
+                    Err(content) => content,
+                },
+                NodeChild::Data(d) => [NodeChild::Data(d)].into(),
+            })
+            .collect();
+        if let Some((rule, _)) = &self.rule {
+            if rule.skippable() {
+                return Err(childs);
+            }
+
+            if childs.is_empty() {
+                return Err(childs);
+            }
+        }
+        Ok(Self {
+            rule: self.rule,
+            childs,
+        })
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 7de0486..8bd06f0 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,7 +1,7 @@
 mod double_enum;
 mod ll_grammar;
 mod scanner;
-use ll_grammar::{LLGrammar, Sentential};
+use ll_grammar::{LLGrammar, Sentential, Skippable};
 use regex::{Match, Regex};
 use scanner::Scanner;
 use std::collections::HashMap;
@@ -29,6 +29,7 @@ double_enum!(
         Dot,
         Ident(String),
         Int(i64),
+        Str(String),
         Float(f64),
     }
 );
@@ -98,6 +99,9 @@ scanner!(
     r"^[0-9]+.[0-9]*" : |_, m: Match<'_>| {
         m.as_str().parse::<_>().ok().map(|f| Float(f))
     }
+    r#"^"(([^"\\]|(\\[a-z\\"]))*)""# : |capture: regex::Captures<'_>, _| {
+        capture.get(1).map(|m| Str(m.as_str().to_string()))
+    }
     r"^[0-9]+" : |_, m: Match<'_>| {
         m.as_str().parse::<_>().ok().map(|i| Int(i))
     }
@@ -105,16 +109,29 @@ scanner!(
 
 #[derive(Debug, PartialEq, Eq, Hash, Clone)]
 enum NoneTerminals {
-    P, // Program, ; separated
-    L, // Line of code
-    Li, // line extended for assignments
-    IF, // if helper
-    E,  // Expression
-    Ei, // Expression extended additive
-    T,  // Term, only containing Factors
-    Ti, // Term extend multiplicative
-    F,  // Factor
-    FI, // Factor extended with complex types and operators
+    P,   // Program, ; separated
+    L,   // Line of code
+    Li,  // line extended for assignments
+    IF,  // if helper
+    Sem, // optional semicolon
+    E,   // Expression
+    Ei,  // Expression extended additive
+    T,   // math term
+    Ti,  // meth term extended
+    S,   // Summand, only containing Factors
+    Si,  // Summand extend multiplicative
+    F,   // Factor
+    Fi,  // Factor extended with complex types and operators
+}
+
+impl Skippable for NoneTerminals {
+    fn skippable(&self) -> bool {
+        use NoneTerminals::*;
+        match self {
+            P | Li | Ei | Si | Ti | Fi | IF | Sem => true,
+            _ => false,
+        }
+    }
 }
 
 impl<T> From<NoneTerminals> for Sentential<T, NoneTerminals> {
@@ -134,38 +151,50 @@ fn grammer() -> LLGrammar<NoneTerminals, BareTokens> {
     use NoneTerminals::*;
     ll_grammar![
         start: P;
-        P -> L,Semicolon,P;
+        P -> L,P;
         P -> ;
-        L -> While,E,LQBrace,P,RQBrace;
+        L -> While,E,LQBrace,P,RQBrace,Sem;
         L -> If,E,LQBrace,P,RQBrace,IF;
-        IF -> ;
-        IF -> Else,LQBrace,P,RQBrace;
-        L -> Ident,FI,Li;
-        Li -> Assign,E;
-        Li -> ;
+        IF -> Sem;
+        IF -> Else,LQBrace,P,RQBrace,Sem;
+        Sem -> ;
+        Sem -> Semicolon;
+        L -> Ident,Fi,Li;
+        Li -> Assign,E,Semicolon;
+        Li -> Semicolon;
+
         E -> T,Ei;
         Ei -> Eq,T,Ei;
         Ei -> Neq,T,Ei;
-        Ei -> Add,T,Ei;
-        Ei -> Sub,T,Ei;
         Ei -> ;
-        T -> F,Ti;
-        Ti -> Mul,F,Ti;
-        Ti -> Div,F,Ti;
+
+        T -> S,Ti;
+        Ti -> Add,S,Ti;
+        Ti -> Sub,S,Ti;
         Ti -> ;
+
+        S -> F,Si;
+        Si -> Mul,F,Si;
+        Si -> Div,F,Si;
+        Si -> ;
+
         F -> LBrace, E, RBrace;
         F -> Int;
         F -> Float;
-        F -> Ident,FI;
-        FI -> ;
-        FI -> LBrace,E,RBrace;
-        FI -> Dot, FI;
-        FI -> LSBrace,E,RSBrace;
+        F -> Str;
+        F -> Ident,Fi;
+
+        Fi -> ;
+        Fi -> LBrace,E,RBrace;
+        Fi -> Dot, Fi;
+        Fi -> LSBrace,E,RSBrace;
     ]
 }
 
 fn main() {
-    let code = String::from("a = 4; while a != 5 { a = a+1; }; if a == 5 { a = 4; } else {a = 5;};");
+    let code = String::from(
+        "a = 4; while a != 5 { a = (a+1) * 4; }; if a == 5 { a = \"abs123\"; } else {a = 5;}",
+    );
     let mut m = Scanner::<Tokens>::new(code).with_skipping(Tokens::WhiteSpace);
 
     let mut grammar = grammer();
@@ -176,5 +205,11 @@ fn main() {
     println!("conflict: {conflict}");
     println!("prase table: {:?}", grammar.parse_table);
     println!("parse\n\n");
-    println!("parsed: {:?}", grammar.parser(&mut m.iter_mut()).parse())
+    println!(
+        "parsed: {:?}",
+        grammar
+            .parser(&mut m.iter_mut())
+            .parse()
+            .map(|tree| tree.clean())
+    )
 }