pipe, return

src/codegen.rs

@@ -49,9 +49,9 @@ impl Env {
 }
 
 pub trait Codegen {
+    fn get_output(&self) -> String;
     fn emit_prologue(&mut self) -> Result<(), Box<dyn Error>>;
     fn emit_epilogue(&mut self) -> Result<(), Box<dyn Error>>;
-    fn get_output(&self) -> String;
     fn compile_stmt(&mut self, env: &mut Env, stmt: Stmt) -> Result<(), Box<dyn Error>>;
     fn compile_expr(&mut self, env: &mut Env, expr: Expr) -> Result<(), Box<dyn Error>>;
 }

src/codegen_x86_64.rs

@@ -26,6 +26,10 @@ impl CodegenX86_64 {
 }
 
 impl Codegen for CodegenX86_64 {
+    fn get_output(&self) -> String {
+        self.output.clone()
+    }
+
     fn emit_prologue(&mut self) -> Result<(), Box<dyn Error>> {
         writeln!(
             &mut self.output,
@@ -55,10 +59,6 @@ print:
         Ok(())
     }
 
-    fn get_output(&self) -> String {
-        self.output.clone()
-    }
-
     fn compile_stmt(&mut self, env: &mut Env, stmt: Stmt) -> Result<(), Box<dyn Error>> {
         match stmt {
             Stmt::Expression(expr) => self.compile_expr(env, expr)?,
@@ -121,9 +121,15 @@ print:
 
                 self.compile_stmt(env, *body)?;
 
+                writeln!(&mut self.output, "    mov rax, 0")?;
+                writeln!(&mut self.output, "    mov rsp, rbp")?;
+                writeln!(&mut self.output, "    pop rbp")?;
+                writeln!(&mut self.output, "    ret")?;
+            }
+            Stmt::Return(expr) => {
+                self.compile_expr(env, expr)?;
                 writeln!(&mut self.output, "    mov rsp, rbp")?;
                 writeln!(&mut self.output, "    pop rbp")?;
-                writeln!(&mut self.output, "    mov rax, 0")?;
                 writeln!(&mut self.output, "    ret")?;
             }
         }
@@ -245,10 +251,12 @@ print:
                 };
 
                 // TODO
-                assert!(args.len() == 1);
+                assert!(args.len() <= 1);
+                if args.len() == 1 {
+                    self.compile_expr(env, args.first().unwrap().clone())?;
+                    writeln!(&mut self.output, "    mov rdi, rax")?;
+                }
 
-                self.compile_expr(env, args.first().unwrap().clone())?;
-                writeln!(&mut self.output, "    mov rdi, rax")?;
                 writeln!(&mut self.output, "    call {}", callee)?;
             }
         }

src/parser.rs

@@ -31,6 +31,7 @@ pub enum Stmt {
         params: Vec<Param>,
         body: Box<Stmt>,
     },
+    Return(Expr),
 }
 
 #[derive(Debug, Clone)]
@@ -139,11 +140,17 @@ impl Parser {
             self.if_statement()
         } else if self.match_token(&[TokenType::KeywordWhile]) {
             self.while_statement()
+        } else if self.match_token(&[TokenType::KeywordReturn]) {
+            self.return_statement()
         } else {
             Ok(Stmt::Expression(self.expression()?))
         }
     }
 
+    fn return_statement(&mut self) -> Result<Stmt, Box<dyn Error>> {
+        Ok(Stmt::Return(self.expression()?))
+    }
+
     fn if_statement(&mut self) -> Result<Stmt, Box<dyn Error>> {
         let condition = self.expression()?;
         let then_branch = self.block()?;
@@ -177,7 +184,7 @@ impl Parser {
     }
 
     fn assignment(&mut self) -> Result<Expr, Box<dyn Error>> {
-        let expr = self.logical_or()?;
+        let expr = self.pipe()?;
 
         if self.match_token(&[TokenType::Equal]) {
             let equals = self.previous().clone();
@@ -195,6 +202,36 @@ impl Parser {
         Ok(expr)
     }
 
+    fn pipe(&mut self) -> Result<Expr, Box<dyn Error>> {
+        let mut expr = self.logical_or()?;
+
+        while self.match_token(&[TokenType::Pipe]) {
+            let pipe = self.previous().clone();
+            let right = self.equality()?;
+
+            match right {
+                Expr::Call {
+                    callee,
+                    paren,
+                    args,
+                } => {
+                    let mut new_args = args;
+                    new_args.insert(0, expr);
+                    expr = Expr::Call {
+                        callee,
+                        paren,
+                        args: new_args,
+                    }
+                }
+                _ => {
+                    return error!(pipe.loc, "tried to pipe into a non-call expression");
+                }
+            };
+        }
+
+        Ok(expr)
+    }
+
     fn logical_or(&mut self) -> Result<Expr, Box<dyn Error>> {
         let mut expr = self.logical_and()?;
 

src/tokenizer.rs

@@ -17,6 +17,7 @@ pub enum TokenType {
     Colon,
     And,
     Or,
+    Pipe,
 
     Equal,
     DoubleEqual,
@@ -35,6 +36,7 @@ pub enum TokenType {
     KeywordElse,
     KeywordWhile,
     KeywordFunc,
+    KeywordReturn,
 
     Indent,
     Dedent,
@@ -159,8 +161,10 @@ impl Tokenizer {
             '|' => {
                 if self.match_char('|') {
                     self.add_token(TokenType::Or);
+                } else if self.match_char('>') {
+                    self.add_token(TokenType::Pipe);
                 } else {
-                    return error!(self.loc, "expected '|' after '|'");
+                    return error!(self.loc, "expected '>' or '|' after '|'");
                 }
             }
             '!' => {
@@ -300,6 +304,7 @@ impl Tokenizer {
             "else" => TokenType::KeywordElse,
             "while" => TokenType::KeywordWhile,
             "func" => TokenType::KeywordFunc,
+            "return" => TokenType::KeywordReturn,
             _ => TokenType::Identifier,
         })
     }