diff --git a/src/frontend/mod.rs b/src/frontend/mod.rs
index 565d9e9..a27d605 100644
--- a/src/frontend/mod.rs
+++ b/src/frontend/mod.rs
@@ -1,4 +1,4 @@
 pub mod types;
-mod lexer;
+pub mod lexer;
 pub mod parser;
 pub mod err;
\ No newline at end of file
diff --git a/src/frontend/parser.rs b/src/frontend/parser.rs
index 7359101..d20d164 100644
--- a/src/frontend/parser.rs
+++ b/src/frontend/parser.rs
@@ -12,7 +12,7 @@ use crate::{
 
 pub struct Parser {
     tokens: Vec<Token>,
-    diagnostics: Diagnositics,
+    pub diagnostics: Diagnositics,
     pos: usize,
 }
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -31,7 +31,9 @@ impl Parser {
             pos: 0,
         }
     }
-    pub fn parse(&mut self) {}
+    pub fn parse(&mut self) -> CompileUnit {
+        self.parse_compile_unit()
+    }
     fn peek(&self) -> Option<&Token> {
         self.tokens.get(self.pos)
     }
@@ -366,10 +368,68 @@ impl Parser {
         assert!(self.peek().is_some());
         let token = self.next().unwrap().clone();
         match token.value {
-            TokenValue::Ident(name) => Some(Expr {
-                value: ExprValue::Var(name),
-                span: token.span,
-            }),
+            TokenValue::Ident(name) => {
+                if self
+                    .peek()
+                    .is_some_and(|t| matches!(t.value, TokenValue::LParen))
+                {
+                    self.advance(1);
+                    let mut args = vec![];
+                    loop {
+                        match self.peek() {
+                            Some(t) if matches!(t.value, TokenValue::RParen) => {
+                                let end_span = t.span;
+                                self.advance(1);
+                                return Some(Expr {
+                                    value: ExprValue::FuncCall(name, args),
+                                    span: Span::from_two(token.span, end_span),
+                                });
+                            }
+                            Some(_) => {}
+                            None => {
+                                self.diagnostics.add_from_frontend_error(
+                                    ParseError::ExpectButEof("`)`"),
+                                    token.span,
+                                );
+                                return None;
+                            }
+                        }
+                        args.push(self.parse_expr()?);
+                        match self.peek() {
+                            Some(t) if matches!(t.value, TokenValue::Comma) => {
+                                self.advance(1);
+                            }
+                            Some(t) if matches!(t.value, TokenValue::RParen) => {
+                                let end_span = t.span;
+                                self.advance(1);
+                                return Some(Expr {
+                                    value: ExprValue::FuncCall(name, args),
+                                    span: Span::from_two(token.span, end_span),
+                                });
+                            }
+                            Some(_) => {
+                                let token = self.next().unwrap().clone();
+                                self.diagnostics.add_from_frontend_error(
+                                    ParseError::UnexpectedToken(token.value, "`,` or `)`"),
+                                    token.span,
+                                );
+                                return None;
+                            }
+                            None => {
+                                self.diagnostics.add_from_frontend_error(
+                                    ParseError::ExpectButEof("`)`"),
+                                    token.span,
+                                );
+                                return None;
+                            }
+                        }
+                    }
+                }
+                Some(Expr {
+                    value: ExprValue::Var(name),
+                    span: token.span,
+                })
+            },
             TokenValue::IntLit(value) => Some(Expr {
                 value: ExprValue::IntLit(value),
                 span: token.span,
@@ -709,4 +769,4 @@ mod tests {
         test_case("0-3,14-25");
         // test_case("0-3,14-25");
     }
-}
\ No newline at end of file
+}