diff --git a/src/ll_grammar.rs b/src/ll_grammar.rs
index 75a24aa..819607f 100644
--- a/src/ll_grammar.rs
+++ b/src/ll_grammar.rs
@@ -289,7 +289,7 @@ impl<N: PartialEq + Eq + Hash + Clone, T: PartialEq + Eq + Hash + Clone> LLGramm
         &self,
         none_terminal: &N,
         terminal: &Option<T>,
-    ) -> Option<&Vec<Sentential<T, N>>> {
+    ) -> Option<(usize, &Vec<Sentential<T, N>>)> {
         assert!(
             self.parse_table.is_some(),
             "Please call gen_parse_table before this!"
@@ -298,12 +298,17 @@ impl<N: PartialEq + Eq + Hash + Clone, T: PartialEq + Eq + Hash + Clone> LLGramm
             .as_ref()
             .unwrap()
             .get(&(none_terminal.clone(), terminal.clone()))
-            .and_then(|f| self.rules.get(none_terminal).and_then(|rule| rule.get(*f)))
+            .and_then(|f| {
+                self.rules
+                    .get(none_terminal)
+                    .and_then(|rule| rule.get(*f))
+                    .map(|rule| (*f, rule))
+            })
     }
 
-    pub fn create_checker<'a, S: Into<T> + PartialEq<T> + Clone>(
+    pub fn parser<'a, S: Into<T> + PartialEq<T> + Clone>(
         &'a self,
-        iter: &'a mut dyn Iterator<Item = S>,
+        iter: &'a mut dyn Iterator<Item = Result<S, String>>,
     ) -> LLTabelParser<N, T, S> {
         assert!(
             self.parse_table.is_some(),
@@ -324,7 +329,7 @@ pub struct LLTabelParser<
     S: Into<T> + PartialEq<T> + Clone,
 > {
     grammar: &'a LLGrammar<N, T>,
-    input: &'a mut dyn Iterator<Item = S>,
+    input: &'a mut dyn Iterator<Item = Result<S, String>>,
 }
 
 impl<
@@ -334,49 +339,121 @@ impl<
         S: Into<T> + PartialEq<T> + Clone + Debug,
     > LLTabelParser<'a, N, T, S>
 {
-    pub fn parse(&mut self) -> bool {
-        let mut stack: Vec<Sentential<Option<T>, N>> = vec![
-            Sentential::Terminal(None),
-            Sentential::NoneTerminal(self.grammar.start.clone()),
-        ];
-        let mut next = self.input.next();
+    pub fn parse(&mut self) -> Result<ParseTree<N, S>, String> {
+        // stack of table driven parser
+        // content of the vec:
+        // - first element: all of them combined represent the complete stack, of the parser.
+        // - secount element: rule has to able to derive the code defined, by its inner childs and the unparsed code from the accompanying first element.
+        let mut stack: Vec<(Vec<Sentential<T, N>>, ParseTree<N, S>)> = vec![(
+            vec![Sentential::NoneTerminal(self.grammar.start.clone())],
+            ParseTree::new(None),
+        )];
+
+        let mut next = match self.input.next() {
+            Some(Ok(d)) => Some(d),
+            Some(Err(err)) => return Err(format!("Invalid token: {}", err)),
+            None => None,
+        };
+
         loop {
-            if next.is_none() {
-                println!("EOF");
-                return self.input.size_hint().0 == 0;
-            }
-            let state = stack.pop();
-            match state {
-                Some(Sentential::Terminal(t)) => match (next, t) {
-                    (Some(a), Some(b)) if a == b => {
-                        next = self.input.next();
+            // look at current state
+            let mut state = stack.pop();
+            match state.as_mut() {
+                // processing inner state, of tracked rules
+                Some((inner_stack, rule)) => {
+                    let inner_state = inner_stack.pop();
+                    match inner_state {
+                        // match terminal, check if equal
+                        Some(Sentential::Terminal(terminal)) => match (next, terminal) {
+                            // actual vs. expected input
+                            (Some(inn), expect) if inn == expect => {
+                                next = match self.input.next() {
+                                    Some(Ok(n)) => Some(n),
+                                    Some(Err(err)) => {
+                                        return Err(format!("Invalid token: {}", err))
+                                    }
+                                    None => None,
+                                };
+                                rule.childs.push(NodeChild::Data(inn));
+                                stack.push(state.unwrap());
+                            }
+                            (a, b) => {
+                                return Err(format!("found: {:?} expected: {:?}", a, b));
+                            }
+                        },
+                        // take next none terminal and apply rule from parse table.
+                        Some(Sentential::NoneTerminal(none_term)) => {
+                            // load rule
+                            let Some((id, new_rule)) = self
+                                .grammar
+                                .parse_table(&none_term, &next.as_ref().map(|f| f.clone().into()))
+                            else {
+                                // no rule
+                                return Err(format!(
+                                    "Unexpected token: {}",
+                                    next.map(|f| format!("{f:?}"))
+                                        .unwrap_or("end of file".to_string())
+                                ));
+                            };
+
+                            // reverse rule: because, uses vec as stack, but reversed
+                            let new_rule_rev =
+                                new_rule.iter().rev().map(|f| f.clone()).collect::<Vec<_>>();
+                            // memorize current state/rule for later
+                            stack.push(state.unwrap());
+                            // process next rule
+                            stack.push((
+                                new_rule_rev,
+                                ParseTree {
+                                    rule: Some((none_term, id)),
+                                    childs: Vec::new(),
+                                },
+                            ));
+                        }
+                        // inner state is empty: current rule is finished
+                        None => {
+                            // if stack is empty, this is the initial state: finish or err
+                            let Some(last) = stack.last_mut() else {
+                                // ok: input has ended
+                                if next.is_none() {
+                                    return Ok(state.unwrap().1);
+                                }
+                                // still code left, but not excepted
+                                return Err(format!("Expected end of file."));
+                            };
+                            last.1.childs.push(NodeChild::Child(state.unwrap().1));
+                        }
                     }
-                    (None, None) => {
-                        next = self.input.next();
-                    }
-                    (a, b) => {
-                        println!("not matching terminals: {a:?}, {b:?}");
-                        return false;
-                    }
-                },
-                Some(Sentential::NoneTerminal(nt)) => {
-                    let Some(a) = self
-                        .grammar
-                        .parse_table(&nt, &next.as_ref().map(|f| f.clone().into()))
-                    else {
-                        println!("no parse table entry: {nt:?} next: {next:?}");
-                        return false;
-                    };
-                    stack.extend(a.iter().rev().map(|f| match f {
-                        Sentential::Terminal(t) => Sentential::Terminal(Some(t.clone())),
-                        Sentential::NoneTerminal(nt) => Sentential::NoneTerminal(nt.clone()),
-                    }));
                 }
+                // should not be possible, because every other path pushes to the stack back or returns
                 None => {
-                    println!("EOS");
-                    return false;
+                    return Err(format!("Err: EOS"));
                 }
             }
         }
     }
 }
+
+//
+
+#[derive(Debug, Clone)]
+pub enum NodeChild<N, S> {
+    Child(ParseTree<N, S>),
+    Data(S),
+}
+
+#[derive(Debug, Clone)]
+#[allow(dead_code)]
+pub struct ParseTree<N, S> {
+    pub rule: Option<(N, usize)>,
+    pub childs: Vec<NodeChild<N, S>>,
+}
+
+impl<N, S> ParseTree<N, S> {
+    pub fn new(rule: Option<(N, usize)>) -> Self {
+        Self {
+            rule,
+            childs: Vec::new(),
+        }
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index c79990d..d474a6d 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -34,7 +34,7 @@ double_enum!(
 
 scanner!(
     Tokens,
-    r"^\s|\t|\n" : |_,_| {
+    r"^\s|\t|\n|\r" : |_,_| {
         Some(WhiteSpace)
     }
     r"^;" : |_,_| {
@@ -64,6 +64,9 @@ scanner!(
     r"^while" : |_,_| {
         Some(While)
     }
+    r"^if" : |_,_| {
+        Some(If)
+    }
     r"^\(" : |_,_| {
         Some(LBrace)
     }
@@ -98,8 +101,10 @@ scanner!(
 
 #[derive(Debug, PartialEq, Eq, Hash, Clone)]
 enum NoneTerminals {
-    P,  // Program, ; separated
-    E,  // Expression one line
+    P, // Program, ; separated
+    L, // Line of code
+    Li, // line extended for assignments
+    E,  // Expression
     Ei, // Expression extended additive
     T,  // Term, only containing Factors
     Ti, // Term extend multiplicative
@@ -124,11 +129,14 @@ fn grammer() -> LLGrammar<NoneTerminals, BareTokens> {
     use NoneTerminals::*;
     ll_grammar![
         start: P;
-        P -> E,Semicolon,P;
+        P -> L,Semicolon,P;
         P -> ;
+        L -> While,E,LQBrace,P,RQBrace;
+        L -> If,E,LQBrace,P,RQBrace;
+        L -> Ident,FI,Li;
+        Li -> Assign,E;
+        Li -> ;
         E -> T,Ei;
-        E -> While,LBrace,E,RBrace,LQBrace,P,RQBrace;
-        Ei -> Assign,T,Ei;
         Ei -> Eq,T,Ei;
         Ei -> Neq,T,Ei;
         Ei -> Add,T,Ei;
@@ -150,11 +158,8 @@ fn grammer() -> LLGrammar<NoneTerminals, BareTokens> {
 }
 
 fn main() {
-    let code = String::from("a = 4; while(a != 5) {a = a+1;};");
+    let code = String::from("a = 4;while a != 5 { a = a+1; }; if a == 5 { a = 4; };");
     let mut m = Scanner::<Tokens>::new(code).with_skipping(Tokens::WhiteSpace);
-    /* for token in m.iter_mut() {
-        println!("{:?}", token);
-    } */
 
     let mut grammar = grammer();
     grammar.gen_follow();
@@ -163,8 +168,6 @@ fn main() {
     let conflict = grammar.gen_parse_table();
     println!("conflict: {conflict}");
     println!("prase table: {:?}", grammar.parse_table);
-    println!(
-        "parsed: {}",
-        grammar.create_checker(&mut m.iter_mut()).parse()
-    )
+    println!("parse\n\n");
+    println!("parsed: {:?}", grammar.parser(&mut m.iter_mut()).parse())
 }
diff --git a/src/scanner.rs b/src/scanner.rs
index bf2223f..c7025ea 100644
--- a/src/scanner.rs
+++ b/src/scanner.rs
@@ -1,4 +1,4 @@
-use std::{iter::Peekable, marker::PhantomData};
+use std::marker::PhantomData;
 
 #[macro_export]
 macro_rules! scanner {
@@ -33,6 +33,7 @@ pub struct Scanner<T: MatchNext<T> + PartialEq> {
     _a: PhantomData<T>,
 }
 
+#[allow(dead_code)]
 impl<T: MatchNext<T> + PartialEq> Scanner<T> {
     pub fn new(code: String) -> Self {
         Self {
@@ -55,8 +56,8 @@ impl<T: MatchNext<T> + PartialEq> Scanner<T> {
 
 pub struct ScannerIter<'a, T: MatchNext<T> + PartialEq>(&'a mut Scanner<T>);
 
-impl<'a, T: MatchNext<T> + PartialEq> Iterator for ScannerIter<'a, T> {
-    type Item = T;
+impl<'a, T: MatchNext<T> + PartialEq + std::fmt::Debug> Iterator for ScannerIter<'a, T> {
+    type Item = Result<T, String>;
 
     fn next(&mut self) -> Option<Self::Item> {
         if self.0.code.is_empty() {
@@ -68,9 +69,15 @@ impl<'a, T: MatchNext<T> + PartialEq> Iterator for ScannerIter<'a, T> {
                 if self.0.skip.contains(&token) {
                     continue;
                 }
-                return Some(token);
+                return Some(Ok(token));
             }
-            return None;
+            return self
+                .0
+                .code
+                .split(" ")
+                .collect::<Vec<_>>()
+                .first()
+                .map(|f| Err(f.to_string()));
         }
     }
     fn size_hint(&self) -> (usize, Option<usize>) {