commit b6117ec12d641a61c745fa70768e8ef5f0921806
Author: Michael Sippel <micha@fragmental.art>
Date:   Sun Oct 1 13:11:29 2023 +0200

    initial lexer

diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..0a57fd3
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+authors = ["Michael Sippel <micha@fragmental.art>"]
+edition = "2018"
+name = "laddertypes"
+version = "0.1.0"
+
diff --git a/src/lexer.rs b/src/lexer.rs
new file mode 100644
index 0000000..93039e1
--- /dev/null
+++ b/src/lexer.rs
@@ -0,0 +1,147 @@
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+#[derive(PartialEq, Eq, Clone, Debug)]
+pub enum LadderTypeToken {
+    Symbol( String ),
+    Char( char ),
+    Num( u64 ),
+    Open,
+    Close,
+    Ladder,
+}
+
+#[derive(PartialEq, Eq, Clone, Debug)]
+pub enum LexError {
+    /// found a non-digit character inside a numeric token
+    InvalidDigit,
+
+    /// quoted character token didnt close correctly with '
+    InvalidChar,
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+#[derive(PartialEq, Eq, Clone, Debug)]
+enum LexerState {
+    Any,
+    Sym( String ),
+    Num( u64 ),
+    Char( Option<char> )
+}
+
+impl LexerState {
+    fn into_token(self) -> Option<LadderTypeToken> {
+        match self {
+            LexerState::Any => None,
+            LexerState::Sym(s) => Some(LadderTypeToken::Symbol(s)),
+            LexerState::Num(n) => Some(LadderTypeToken::Num(n)),
+            LexerState::Char(c) => Some(LadderTypeToken::Char(c?))
+        }
+    }
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+pub struct LadderTypeLexer<It>
+where It: std::iter::Iterator<Item = char>
+{
+    chars: std::iter::Peekable<It>,
+}
+
+impl<It> LadderTypeLexer<It>
+where It: Iterator<Item = char>
+{
+    pub fn new(chars: It) -> Self {
+        LadderTypeLexer {
+            chars: chars.peekable()
+        }
+    }
+}
+
+impl<It> Iterator for LadderTypeLexer<It>
+where It: Iterator<Item = char>
+{
+    type Item = Result<LadderTypeToken, LexError>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let mut state = LexerState::Any;
+
+        while let Some(c) = self.chars.peek() {
+            match &mut state {
+
+                // determine token type
+                LexerState::Any => {
+                    match c {
+                        '<' => { self.chars.next(); return Some(Ok(LadderTypeToken::Open)); },
+                        '>' => { self.chars.next(); return Some(Ok(LadderTypeToken::Close)); },
+                        '~' => { self.chars.next(); return Some(Ok(LadderTypeToken::Ladder)); },
+                        '\'' => { self.chars.next(); state = LexerState::Char(None); },
+                        ' ' => { self.chars.next(); },
+                        c => {
+                            if c.is_alphabetic() {
+                                state = LexerState::Sym( String::new() );
+                            } else if c.is_digit(10) {
+                                state = LexerState::Num( 0 );
+                            }
+                        }
+                    }
+                }
+
+                LexerState::Char(val) => {
+                    // todo escape characters
+                    *val = self.chars.next();
+
+                    match self.chars.next() {
+                        Some('\'') => {
+                            if let Some(token) = state.clone().into_token() {
+                                return Some(Ok(token));
+                            }                            
+                        }
+                        _ => {
+                            return Some(Err(LexError::InvalidChar));
+                        }
+                    }
+                }
+
+                _ => {
+
+                    if c.is_whitespace() || *c == '>' || *c == '~' {
+                        // finish the current token
+
+                        if let Some(token) = state.clone().into_token() {
+                            return Some(Ok(token));
+                        }
+                    } else {
+                        // append to the current token
+
+                        let c = self.chars.next().unwrap();
+
+                        match &mut state {
+                            LexerState::Sym(s) => {
+                                s.push(c);
+                            }
+
+                            LexerState::Num(n) => {
+                                if let Some(d) = c.to_digit(10) {
+                                    *n = (*n) * 10 + d as u64;
+                                } else {
+                                    return Some(Err(LexError::InvalidDigit));
+                                }
+                            }
+
+                            _ => {}
+                        }
+                    }
+                }
+            }
+        }
+
+        if let Some(token) = state.into_token() {
+            Some(Ok(token))
+        } else {
+            None
+        }
+    }
+}
+
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..bae0eed
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,139 @@
+
+pub mod lexer;
+//pub mod bimap;
+//pub mod dict;
+//pub mod term;
+
+pub use {
+//    dict::*,
+//    term::*,
+};
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_lexer() {
+        use crate::lexer::*;
+
+        {
+            let mut lex = LadderTypeLexer::new("symbol".chars());
+
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("symbol".into()))) );
+            assert_eq!( lex.next(), None );
+        }
+        {
+            let mut lex = LadderTypeLexer::new("1234".chars());
+
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Num(1234))) );
+            assert_eq!( lex.next(), None );
+        }
+        {
+            let mut lex = LadderTypeLexer::new("123xxx".chars());
+            assert_eq!( lex.next(), Some(Err(LexError::InvalidDigit)) );
+        }
+        {
+            let mut lex = LadderTypeLexer::new("'x'".chars());
+
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Char('x'))) );
+            assert_eq!( lex.next(), None );
+        }
+        {
+            let mut lex = LadderTypeLexer::new("'xx'".chars());
+            assert_eq!( lex.next(), Some(Err(LexError::InvalidChar)) );
+        }
+        {
+            let mut lex = LadderTypeLexer::new("abc~def".chars());
+
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("abc".into()))) );
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Ladder)) );
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("def".into()))) );
+            assert_eq!( lex.next(), None );
+        }
+        {
+            let mut lex = LadderTypeLexer::new("abc   ~ def".chars());
+
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("abc".into()))) );
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Ladder)) );
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("def".into()))) );
+            assert_eq!( lex.next(), None );
+        }
+
+        {
+            let mut lex = LadderTypeLexer::new("<Seq Char>".chars());
+
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Open)) );
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("Seq".into()))) );
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("Char".into()))) );
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Close)) );
+            assert_eq!( lex.next(), None );
+        }
+        {
+            let mut lex = LadderTypeLexer::new("   <Seq      Char  >".chars());
+
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Open)) );
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("Seq".into()))) );
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("Char".into()))) );
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Close)) );
+            assert_eq!( lex.next(), None );
+        }
+
+        {
+            let mut lex = LadderTypeLexer::new("<Seq Date~<TimeSince UnixEpoch>~<Duration Seconds>~ℕ~<PosInt 10 BigEndian>~<Seq <Digit 10>~Unicode>".chars());
+
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Open)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("Seq".into()))));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("Date".into()))));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Ladder)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Open)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("TimeSince".into()))));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("UnixEpoch".into()))));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Close)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Ladder)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Open)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("Duration".into()))));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("Seconds".into()))));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Close)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Ladder)));            
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("ℕ".into()))));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Ladder)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Open)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("PosInt".into()))));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Num(10))));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("BigEndian".into()))));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Close)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Ladder)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Open)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("Seq".into()))));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Open)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("Digit".into()))));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Num(10))));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Close)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Ladder)));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Symbol("Unicode".into()))));
+            assert_eq!( lex.next(), Some(Ok(LadderTypeToken::Close)));
+            assert_eq!( lex.next(), None );
+        }
+    }
+
+    #[test]
+    fn test_parse() {
+        // todo
+    }
+
+    #[test]
+    fn test_normalize() {
+        // todo
+    }
+    
+    #[test]
+    fn test_curry() {
+        // todo
+    }
+
+    #[test]
+    fn test_subtype() {
+        // todo
+    }
+}
+
+