added strings! applied clippy recs

src/evaluator/mod.rs

@@ -54,6 +54,7 @@ impl Environment {
 #[derive(Debug, Clone, PartialEq)]
 pub enum Object {
     Integer(i64),
+    String(String),
     Boolean(bool),
     ReturnValue(Box<Object>),
     Error(String),
@@ -69,6 +70,7 @@ impl Object {
     pub fn inspect(&self) -> String {
         match self {
             Object::Integer(v) => v.to_string(),
+            Object::String(s) => s.to_string(),
             Object::Boolean(v) => v.to_string(),
             Object::ReturnValue(ret) => ret.inspect(),
             Object::Error(s) => s.to_string(),
@@ -79,7 +81,7 @@ impl Object {
                 out.write_fmt(format_args!(
                     "fn({}) {{ {} }}",
                     s.parameters.iter().map(|x| x.to_string()).join(", "),
-                    s.body.to_string()
+                    s.body
                 ))
                 .unwrap();
 
@@ -93,6 +95,7 @@ impl Display for Object {
     fn fmt(&self, f: &mut Formatter) -> FmtResult {
         f.write_str(match self {
             Object::Integer(_) => "INTEGER",
+            Object::String(_) => "STRING",
             Object::Boolean(_) => "BOOLEAN",
             Object::ReturnValue(_) => "RETURN_VALUE",
             Object::Error(_) => "ERROR",
@@ -195,6 +198,23 @@ mod tests {
         run_test_cases(&test_cases);
     }
 
+    #[test]
+    fn eval_string_literal_expression() {
+        let test_cases = [("\"Hello \"", Some(Object::String("Hello ".to_owned())))];
+
+        run_test_cases(&test_cases);
+    }
+
+    #[test]
+    fn eval_string_concatenation() {
+        let test_cases = [(
+            "\"Hello \" + \"World\"",
+            Some(Object::String("Hello World".to_owned())),
+        )];
+
+        run_test_cases(&test_cases);
+    }
+
     #[test]
     fn eval_if_else_expression() {
         let test_cases = [
@@ -280,6 +300,10 @@ mod tests {
                 "foobar",
                 Some(Object::Error("identifier not found: foobar".into())),
             ),
+            (
+                "\"Hello\" - \"World\"",
+                Some(Object::Error("unknown operator: STRING - STRING".into())),
+            ),
         ];
 
         run_test_cases(&test_cases);
@@ -304,7 +328,7 @@ mod tests {
     fn test_function_object() {
         let test_case = "fn(x) { x + 2;};";
 
-        let lexer = Lexer::new(&test_case);
+        let lexer = Lexer::new(test_case);
         let mut parser = Parser::new(lexer);
         let program = parser.parse_program();
         assert!(program.is_some());
@@ -373,7 +397,7 @@ mod tests {
         // even though it is never used.
         let test_cases = [(
             "let counter = fn(x) {
-                if (x > 100 ) {
+                if (x > 30 ) {
                     return true;
                 } else {
                     let foobar = 9999;

src/evaluator/tree_walker.rs

@@ -46,6 +46,7 @@ impl Evaluator for TreeWalker {
             Node::Expression(expr) => match expr {
                 Expression::Identifier(v) => self.eval_identifier(v, env),
                 Expression::IntegerLiteral(il) => Some(Object::Integer(il.value)),
+                Expression::StringLiteral(s) => Some(Object::String(s.value)),
                 Expression::BooleanExpression(b) => Some(Object::Boolean(b.value)),
                 Expression::PrefixExpression(p) => {
                     let expr = self.eval(Node::Expression(*p.right), env)?;
@@ -56,13 +57,11 @@ impl Evaluator for TreeWalker {
                     let right = self.eval(Node::Expression(*ie.right), env)?;
                     self.eval_infix_expression(left, ie.operator, right)
                 }
-                Expression::FunctionExpression(fnl) => {
+                Expression::FunctionExpression(fnl) => Some(Object::Function(Function {
-                    return Some(Object::Function(Function {
                     body: fnl.body,
                     parameters: fnl.parameters,
-                        env: env,
+                    env,
-                    }));
+                })),
-                }
                 Expression::CallExpression(v) => {
                     let function = self.eval(Node::Expression(*v.function), env.clone())?;
                     // Resolve function arguments and update the environment
@@ -179,6 +178,9 @@ impl TreeWalker {
                 TokenType::LessThan => Object::Boolean(l < r),
                 _ => Object::Error(format!("unknown operator: {} {} {}", l, operator, r)),
             },
+            (Object::String(l), Object::String(r)) if operator == TokenType::Plus => {
+                Object::String(l.to_owned() + &r)
+            }
             (o1, o2) if o1.to_string() != o2.to_string() => {
                 Object::Error(format!("type mismatch: {} {} {}", o1, operator, o2))
             }

src/lexer.rs

@@ -31,6 +31,7 @@ pub enum TokenType {
     // by other variants of this enum.
     Ident,
     Int,
+    String,
     // Operators
     Assign,
     Plus,
@@ -91,6 +92,7 @@ impl Display for TokenType {
             TokenType::Illegal => "illegal",
             TokenType::Ident => "ident",
             TokenType::Int => "int",
+            TokenType::String => "string",
         })
     }
 }
@@ -199,6 +201,19 @@ impl<'a> Lexer<'a> {
         }
         number.into_iter().collect()
     }
+
+    fn read_string(&mut self) -> String {
+        let mut out = String::new();
+
+        while let Some(c) = self.read_char() {
+            if c == '"' {
+                break;
+            }
+            out.push(c);
+        }
+
+        out
+    }
 }
 
 impl<'a> Iterator for Lexer<'a> {
@@ -210,10 +225,7 @@ impl<'a> Iterator for Lexer<'a> {
 
         match ch {
             Some('=') => {
-                let is_e = match self.input.peek() {
+                let is_e = matches!(self.input.peek(), Some(v) if *v == '=');
-                    Some(v) if *v == '=' => true,
-                    _ => false,
-                };
                 if is_e {
                     self.read_char();
                     Some(token!(TokenType::Equals))
@@ -232,10 +244,7 @@ impl<'a> Iterator for Lexer<'a> {
             Some('{') => Some(token!(TokenType::LBrace)),
             Some('}') => Some(token!(TokenType::RBrace)),
             Some('!') => {
-                let is_ne = match self.input.peek() {
+                let is_ne = matches!(self.input.peek(), Some(v) if *v == '=');
-                    Some(v) if *v == '=' => true,
-                    _ => false,
-                };
                 if is_ne {
                     self.read_char();
                     Some(token!(TokenType::NotEquals))
@@ -245,6 +254,10 @@ impl<'a> Iterator for Lexer<'a> {
             }
             Some('>') => Some(token!(TokenType::GreaterThan)),
             Some('<') => Some(token!(TokenType::LessThan)),
+            Some('"') => {
+                let str = self.read_string();
+                Some(token!(TokenType::String, &str))
+            }
             Some(ch) if is_letter(ch) => {
                 let ident = self.read_identifier(ch);
                 Some(lookup_ident(&ident))
@@ -364,6 +377,9 @@ mod tests {
                 10 == 10;
                 9 != 10;
 
+                \"foobar\"
+                \"foo bar\"
+
                 "
             )
             .collect::<Vec<Token>>(),
@@ -415,6 +431,8 @@ mod tests {
                 token!(TokenType::NotEquals),
                 token!(TokenType::Int, "10"),
                 token!(TokenType::Semicolon),
+                token!(TokenType::String, "foobar"),
+                token!(TokenType::String, "foo bar"),
                 token!(TokenType::EOF),
             ],
         );

src/main.rs

@@ -1,3 +1,4 @@
+#![feature(assert_matches)]
 #[macro_use]
 extern crate lazy_static;
 

src/parser/ast.rs

@@ -102,7 +102,7 @@ impl LetStatement {
 
 impl Display for LetStatement {
     fn fmt(&self, f: &mut Formatter) -> FmtResult {
-        let mut out = format!("{} {} = ", TokenType::Let.to_string(), self.name.value);
+        let mut out = format!("{} {} = ", TokenType::Let, self.name.value);
 
         if let Some(v) = &self.value {
             let a: String = v.into();
@@ -188,6 +188,7 @@ pub enum ExpressionPriority {
 pub enum Expression {
     Identifier(Identifier),
     IntegerLiteral(IntegerLiteral),
+    StringLiteral(StringLiteral),
     PrefixExpression(PrefixExpression),
     InfixExpression(InfixExpression),
     BooleanExpression(BooleanExpression),
@@ -242,6 +243,7 @@ impl Display for Expression {
         let value = match self {
             Expression::Identifier(v) => v.to_string(),
             Expression::IntegerLiteral(v) => v.value.to_string(),
+            Expression::StringLiteral(v) => v.value.to_string(),
             Expression::PrefixExpression(v) => v.to_string(),
             Expression::InfixExpression(v) => v.to_string(),
             Expression::BooleanExpression(v) => v.to_string(),
@@ -313,6 +315,24 @@ impl IntegerLiteral {
     }
 }
 
+#[derive(Debug, PartialEq, Eq, Clone)]
+pub struct StringLiteral {
+    pub value: String,
+}
+
+impl StringLiteral {
+    pub fn new(v: &str) -> Self {
+        Self {
+            value: v.to_string(),
+        }
+    }
+    pub fn parse(_parser: &mut Parser, token: Token) -> Option<Expression> {
+        Some(Expression::StringLiteral(StringLiteral::new(
+            &token.literal?,
+        )))
+    }
+}
+
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub struct PrefixExpression {
     pub operator: TokenType,
@@ -339,11 +359,7 @@ impl PrefixExpression {
 
 impl Display for PrefixExpression {
     fn fmt(&self, f: &mut Formatter) -> FmtResult {
-        f.write_fmt(format_args!(
+        f.write_fmt(format_args!("({}{})", self.operator, self.right))
-            "({}{})",
-            self.operator,
-            self.right.to_string()
-        ))
     }
 }
 
@@ -376,9 +392,7 @@ impl Display for InfixExpression {
     fn fmt(&self, f: &mut Formatter) -> FmtResult {
         f.write_fmt(format_args!(
             "({} {} {})",
-            self.left.to_string(),
+            self.left, self.operator, self.right,
-            self.operator,
-            self.right.to_string(),
         ))
     }
 }
@@ -449,13 +463,9 @@ impl IfExpression {
 
 impl Display for IfExpression {
     fn fmt(&self, f: &mut Formatter) -> FmtResult {
-        let mut out = format!(
+        let mut out = format!("if {} {{ {} }}", self.condition, self.consequence);
-            "if {} {{ {} }}",
-            self.condition.to_string(),
-            self.consequence.to_string()
-        );
         if let Some(alternative) = &self.alternative {
-            out += &format!(" else {{ {} }}", alternative.to_string());
+            out += &format!(" else {{ {} }}", alternative);
         }
         f.write_str(&out)
     }

src/parser/mod.rs

@@ -48,6 +48,7 @@ impl<'a> Parser<'a> {
             infix_parse_fns: HashMap::new(),
         };
 
+        parser.register_prefix(TokenType::String, StringLiteral::parse);
         parser.register_prefix(TokenType::Ident, Identifier::parse);
         parser.register_prefix(TokenType::Int, IntegerLiteral::parse);
         parser.register_prefix(TokenType::Bang, PrefixExpression::parse);
@@ -101,10 +102,7 @@ impl<'a> Parser<'a> {
         if self.peek_token_is(token) {
             self.lexer.next()
         } else {
-            let got_token = match self.lexer.peek() {
+            let got_token = self.lexer.peek().map(|v| v.name);
-                Some(v) => Some(v.name),
-                None => None,
-            };
             self.peek_error(token, got_token);
             None
         }
@@ -113,10 +111,7 @@ impl<'a> Parser<'a> {
     fn peek_error(&mut self, et: TokenType, gt: Option<TokenType>) {
         let msg = match gt {
             Some(v) => format!("expected next token to be {:?}, Got {:?} instead", et, v),
-            None => format!(
+            None => format!("expected next token to be {}, Got None instead", et),
-                "expected next token to be {}, Got None instead",
-                et.to_string()
-            ),
         };
         self.errors.push(Error { reason: msg });
     }
@@ -131,7 +126,7 @@ impl<'a> Parser<'a> {
 
     fn no_prefix_parse_fn_error(&mut self, token: TokenType) {
         self.errors.push(Error {
-            reason: format!("no prefix parse function for {} found", token.to_string()),
+            reason: format!("no prefix parse function for {} found", token),
         });
     }
 
@@ -288,6 +283,24 @@ mod tests {
         );
     }
 
+    #[test]
+    fn string_literal_expression() {
+        let lexer = Lexer::new("\"hello world\";");
+        let mut parser = Parser::new(lexer);
+        let program = parser.parse_program();
+        check_parser_errors(&parser);
+        assert_eq!(parser.errors.len(), 0);
+        assert!(program.is_some());
+
+        assert_eq!(
+            program.unwrap().statements,
+            vec![Statement::ExpressionStatement(ExpressionStatement::new(
+                token!(TokenType::String, "hello world"),
+                Expression::StringLiteral(StringLiteral::new("hello world"))
+            ))]
+        );
+    }
+
     #[test]
     fn prefix_expressions() {
         let test_cases = [