From 99e462f4b5355537941dc70255054e7e09e9f275 Mon Sep 17 00:00:00 2001
From: Daniel M <daniel.q.mueller@stud.h-da.de>
Date: Wed, 2 Feb 2022 14:05:58 +0100
Subject: [PATCH] Implement print keyword

---
 README.md          |  2 +-
 src/interpreter.rs | 19 ++++++++++++++++---
 src/lexer.rs       |  5 +++++
 src/parser.rs      | 14 ++++++++++++++
 4 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 8efbda1..84bc219 100644
--- a/README.md
+++ b/README.md
@@ -45,7 +45,7 @@
 - [x] Line comments `//`
 - [ ] Strings
 - [ ] IO Intrinsics
-  - [ ] Print
+  - [x] Print
   - [ ] ReadLine
 
 ## Grammar
diff --git a/src/interpreter.rs b/src/interpreter.rs
index 2d436b9..2587939 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -1,4 +1,4 @@
-use std::collections::HashMap;
+use std::{collections::HashMap, fmt::Display};
 
 use crate::{parser::{Expression, BinOpType, UnOpType, Ast, Statement, parse}, lexer::lex};
 
@@ -37,8 +37,7 @@ impl Interpreter {
         for stmt in prog.prog {
             match stmt {
                 Statement::Expr(expr) => {
-                    let result = self.resolve_expr(expr);
-                    println!("Result = {:?}", result);
+                    self.resolve_expr(expr);
                 }
 
                 Statement::Loop(lop) => {
@@ -55,6 +54,11 @@ impl Interpreter {
                         }
                     }
                 }
+
+                Statement::Print(expr) => {
+                    let result = self.resolve_expr(expr);
+                    println!("{}", result);
+                }
             }
 
         }
@@ -132,6 +136,15 @@ impl Interpreter {
     }
 }
 
+impl Display for Value {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Value::I64(val) => write!(f, "{}", val),
+        }
+    }
+}
+
+
 #[cfg(test)]
 mod test {
     use super::{Interpreter, Value};
diff --git a/src/lexer.rs b/src/lexer.rs
index 310af6a..f5fb1b4 100644
--- a/src/lexer.rs
+++ b/src/lexer.rs
@@ -10,8 +10,12 @@ pub enum Token {
     /// Identifier (name for variables, functions, ...)
     Ident(String),
 
+    /// Loop keyword (loop)
     Loop,
 
+    /// Print keyword (print)
+    Print,
+
     /// Left Parenthesis ('(')
     LParen,
 
@@ -199,6 +203,7 @@ impl<'a> Lexer<'a> {
 
                     let token = match ident.as_str() {
                         "loop" => Token::Loop,
+                        "print" => Token::Print,
                         _ => Token::Ident(ident),
                     };
 
diff --git a/src/parser.rs b/src/parser.rs
index 9257ed1..244e564 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -95,6 +95,7 @@ pub struct Loop {
 pub enum Statement {
     Expr(Expression),
     Loop(Loop),
+    Print(Expression),
 }
 
 #[derive(Debug, PartialEq, Eq, Clone)]
@@ -142,6 +143,19 @@ impl<T: Iterator<Item = Token>> Parser<T> {
         match self.peek() {
             Token::Loop => Statement::Loop(self.parse_loop()),
 
+            Token::Print => {
+                self.next();
+
+                let expr = self.parse_expr();
+
+                // After a statement, there must be a semicolon
+                if !matches!(self.next(), Token::Semicolon) {
+                    panic!("Expected semicolon after statement");
+                }
+
+                Statement::Print(expr)
+            }
+
             // If it is not a loop, try to lex as an expression
             _ => {
                 let stmt = Statement::Expr(self.parse_expr());