added github as repo

src/language_frontend/parser.rs

@@ -0,0 +1,93 @@
+use chumsky::{combinator::Or, prelude::{choice, just, recursive}, recursive, select, text::{self, ascii::ident}, IterParser, Parser};
+
+use crate::{language_frontend::ast::ast::Expression, language_frontend::tokens::Token};
+
+
+#[allow(clippy::let_and_return)]
+pub fn parser<'src>() -> impl Parser<'src, &'src [Token<'src>], Expression<'src>> {
+    let ident = select! {
+        Token::Ident(ident) => ident
+    };
+
+       let keyword = |kw: &'static str| select! {
+        Token::Keyword(k) if k == kw => ()
+    };
+
+    let eq = just(Token::Equals);
+
+    let expr = recursive(
+        |expr| 
+        {
+            let atom = {
+            let parenthesized = expr
+                .clone()
+                .delimited_by(just(Token::ParenBegin), just(Token::ParenEnd));
+
+            let integer = select! {
+                Token::Integer(n) => Expression::Integer(n),
+            };
+
+            parenthesized.or(integer)
+        };
+
+        let unary = just(Token::Substract)
+            .repeated()
+            .foldr(atom, |_op, rhs| Expression::Negatation(Box::new(rhs)));
+
+        let binary_1 = unary.clone().foldl(
+            just(Token::Multiply)
+                .or(just(Token::Divide))
+                .then(unary)
+                .repeated(),
+            |lhs, (op, rhs)| match op {
+                Token::Multiply => Expression::Multiply(Box::new(lhs), Box::new(rhs)),
+                Token::Divide => Expression::Divide(Box::new(lhs), Box::new(rhs)),
+                _ => unreachable!(),
+            },
+        );
+
+        let binary_2 = binary_1.clone().foldl(
+            just(Token::Add)
+                .or(just(Token::Substract))
+                .then(binary_1)
+                .repeated(),
+            |lhs, (op, rhs)| match op {
+                Token::Add => Expression::Add(Box::new(lhs), Box::new(rhs)),
+                Token::Substract => Expression::Substract(Box::new(lhs), Box::new(rhs)),
+                _ => unreachable!(),
+            },
+        );
+
+        binary_2
+    });
+
+    let decl = recursive(|decl| {
+        let r#var = keyword("var")
+            .ignore_then(ident.clone()) 
+            .then_ignore(eq.clone())
+            .then(decl.clone())
+            .then(decl.clone())
+            .map(|((name, rhs), then)| Expression::Var {
+                name,
+                rhs: Box::new(rhs),
+                then: Box::new(then),
+            });
+
+        let r#fun = keyword("fun")
+            .ignore_then(ident.clone())
+            .then(ident.clone().repeated().collect())
+            .then_ignore(eq.clone())
+            .then(decl.clone())
+            .then(decl.clone())
+            .map(|(((name, args), body), then)| Expression::Function {
+                name,
+                args,
+                body: Box::new(body),
+                then: Box::new(then),
+        });
+        
+        var.or(r#fun).or(expr)
+    });
+
+    decl
+}