for loops and character type

idea.cxpr

@@ -14,6 +14,10 @@ if 49 <~ data {
     println("49 is not the square of a prime");
 }
 
+for p : primes {
+    println(p);
+}
+
 # LET IDENT(square) EQ IDENT(x) ARROW IDENT(x) CARET INT(2) SEMICOLON
 # 
 # LET IDENT(data) EQ IDENT(range) LPAREN INT(100) RPAREN PIPECOLON IDENT(filter) LPAREN IDENT(is_prime) RPAREN PIPECOLON IDENT(map) LPAREN IDENT(square) RPAREN SEMICOLON

src/eval.rs

@@ -55,22 +55,30 @@ impl Environment {
     }
 }
 
+fn unwrap_ident_token<'a>(tok: &'a Token) -> &'a Rc<str> {
+    if let Token { ty: TokenType::Ident(s),.. } = tok {
+        s
+    } else {
+        unreachable!("precondition failed")
+    }
+}
+
 pub fn eval_stmt(stmt: &Stmt, env: EnvRef) -> Result<(), RuntimeError> {
     match stmt {
         Stmt::Expr{ expr } 
             => drop(eval_expr(expr, env)),
-        Stmt::Let { lhs: Token{ty: TokenType::Ident(s),..}, rhs: None } 
+        Stmt::Let { lhs, rhs: None } 
-            => env.borrow_mut().declare(s.clone(), Value::Nil),
+            => env.borrow_mut().declare(unwrap_ident_token(lhs).clone(), Value::Nil),
-        Stmt::Let { lhs: Token{ty: TokenType::Ident(s),..}, rhs: Some(rhs) } => {
+        Stmt::Let { lhs, rhs: Some(rhs) } => {
             let r = eval_expr(rhs, env.clone())?;
-            env.borrow_mut().declare(s.clone(), r)
+            env.borrow_mut().declare(unwrap_ident_token(lhs).clone(), r)
         },
         Stmt::Block { stmts } => {
             let block_env = Environment::extend(env).wrap();
             for stmt in stmts { 
                 eval_stmt(stmt, block_env.clone())? 
             }
-        }
+        },
         Stmt::If { if_clauses, else_clause } => {
             for ic in if_clauses {
                 let cond = eval_expr(&ic.0, env.clone())?;
@@ -81,7 +89,21 @@ pub fn eval_stmt(stmt: &Stmt, env: EnvRef) -> Result<(), RuntimeError> {
             if let Some(ec) = else_clause {
                 return eval_stmt(&ec, env)
             }
-        }
+        },
+        Stmt::For { var, expr, stmt } => {
+            let name = unwrap_ident_token(var);
+            let iter = eval_expr(expr, env.clone())?;
+            env.borrow_mut().declare(name.clone(), Value::Nil);
+            if let Ok(i) = iter.iter() {
+                for v in i {
+                    let env = env.clone();
+                    env.borrow_mut().set(name.clone(), v).expect("unreachable");
+                    eval_stmt(&stmt, env)?;
+                }
+            } else {
+                return Err(RuntimeError { message: "Cannot iterate this type".into(), pos: var.pos.clone() })
+            };
+        },
         _ => unreachable!()
     }
     Ok(())
@@ -111,6 +133,7 @@ pub fn eval_literal(token: &Token) -> Value {
         TokenType::Float(f) => Value::Float(*f),
         TokenType::ImFloat(f) => Value::Complex(Complex64::new(0.0, *f)),
         TokenType::String(s) => Value::String(s.clone()),
+        TokenType::Char(c) => Value::Char(*c),
         _ => todo!()
     }
 }
@@ -147,6 +170,7 @@ pub fn eval_assignment(lhs: &Box<Expr>, rhs: &Box<Expr>, op: &Token, env: EnvRef
                 TokenType::MinusEqual => &prev_value - &r,
                 TokenType::StarEqual => &prev_value * &r,
                 TokenType::SlashEqual => &prev_value / &r,
+                TokenType::PercentEqual => &prev_value % &r,
                 _ => todo!() // TODO more operations
             }.map_err(|e| RuntimeError { message: e, pos: op.pos.clone() })?;
 
@@ -167,6 +191,7 @@ pub fn eval_binary(lhs: &Box<Expr>, rhs: &Box<Expr>, op: &Token, env: EnvRef) ->
         TokenType::Minus => &l - &r,
         TokenType::Star => &l * &r,
         TokenType::Slash => &l / &r,
+        TokenType::Percent => &l % &r,
         _ => todo!() // TODO other operations
     }.map_err(|e| RuntimeError { message: e, pos: op.pos.clone() })
 }

src/expr.rs

@@ -6,7 +6,8 @@ pub enum Stmt {
     Expr { expr: Expr },
     Let { lhs: Token, rhs: Option<Expr> },
     Block { stmts: Vec<Stmt> },
-    If { if_clauses: Vec<(Expr, Stmt)>, else_clause: Option<Box<Stmt>> }
+    If { if_clauses: Vec<(Expr, Stmt)>, else_clause: Option<Box<Stmt>> },
+    For { var: Token, expr: Expr, stmt: Box<Stmt> }
 }
 
 impl fmt::Debug for Stmt {

src/lexer.rs

@@ -66,6 +66,10 @@ impl Lexer {
         }
     }
     
+    fn collect_literal(&self) -> String {
+        self.code[self.start..self.current].iter().collect::<String>()       
+    }
+
     fn advance(&mut self, newline: bool) {
         if newline {
             self.line += 1;
@@ -139,6 +143,7 @@ impl Lexer {
                 },
                 ',' => self.add_token(TokenType::Comma, ","),
                 ';' => self.add_token(TokenType::Semicolon, ";"),
+                ':' => self.add_token(TokenType::Colon, ":"),
                 '(' => self.add_token(TokenType::LParen, "("),
                 ')' => self.add_token(TokenType::RParen, ")"),
                 '[' => self.add_token(TokenType::LBrack, "["),
@@ -152,6 +157,7 @@ impl Lexer {
                     self.advance(true);
                 },
                 '"' => self.string()?,
+                '\'' => self.char()?,
                 ' ' | '\t' | '\r' | '\n' => (),
                 '0'..='9' => self.number()?,
                 'a'..='z' | 'A'..='Z' | '_' => self.ident()?,
@@ -161,6 +167,20 @@ impl Lexer {
         Ok(())
     }
 
+    fn char(&mut self) -> Result<(), ParserError> {
+        if self.at_end() { return Err(self.mk_error("Unexpected EOF in character literal")) }
+        let mut c = self.next();
+        if c == '\'' {
+            return Err(self.mk_error("Empty character literal"))
+        } else if c == '\\' {
+            if self.at_end() { return Err(self.mk_error("Unexpected EOF in character literal")) }
+            // TODO Escapes
+        }
+        self.expect(&['\'']).ok_or(self.mk_error("Expected ' to terminate character literal"))?;
+        self.add_token(TokenType::Char(c), self.collect_literal());
+        Ok(())
+    }
+
     fn string(&mut self) -> Result<(), ParserError> {
         let mut s = String::new();
         while !self.at_end() && self.peek() != '"' {
@@ -188,7 +208,7 @@ impl Lexer {
             return Err(self.mk_error("Unexpected EOF while parsing string"))
         }
         self.advance(false);
-        self.add_token(TokenType::String(Rc::from(s)), self.code[self.start..self.current].iter().collect::<String>());
+        self.add_token(TokenType::String(Rc::from(s)), self.collect_literal());
         Ok(())
     }
 
@@ -206,7 +226,7 @@ impl Lexer {
         }
         let is_imag = !self.at_end() && self.peek() == 'i';
         if is_imag { self.advance(false); }
-        let literal = self.code[self.start..self.current].iter().collect::<String>();
+        let literal = self.collect_literal();
         if is_imag {
             match literal[..literal.len()-1].parse::<f64>() {
                 Ok(num) => self.add_token(TokenType::ImFloat(num), literal),
@@ -230,7 +250,7 @@ impl Lexer {
         while !self.at_end() && (self.peek().is_ascii_alphanumeric() || self.peek() == '_') {
             self.advance(false);
         }
-        let literal = self.code[self.start..self.current].iter().collect::<String>();
+        let literal = self.collect_literal();
         let token_ty = match literal.as_ref() {
             "true" => TokenType::True,
             "false" => TokenType::False,

src/parser.rs

@@ -54,24 +54,28 @@ impl Parser {
         let next = self.peek();
 
         match next.ty {
-            // let statement
             TokenType::Let => {
+                // let statement
                 self.next();
-                return self.letstmt()
+                self.letstmt()
-            }
+            },
             TokenType::LBrace => {
+                // block
                 self.next();
-                return self.block()
+                self.block()
-            }
+            },
-
-            // if statement
             TokenType::If => {
+                // if statement
                 self.next();
-                return self.ifstmt()
+                self.ifstmt()
-            }
+            },
-
+            TokenType::For => {
-            // fallback to an expression terminated with a semicolon
+                // for statement
+                self.next();
+                self.forstmt()
+            },
             _ => {
+                // fallback to an expression terminated with a semicolon
                 let expr = self.assignment()?;
                 if self.at_end() {
                     if self.repl {
@@ -83,10 +87,10 @@ impl Parser {
 
                 let next = self.next();
 
-                return match next.ty {
+                match next.ty {
                     TokenType::Semicolon => Ok(Stmt::Expr{expr}),
                     _ => Err(self.mk_error("Missing semicolon after statement"))
-                };
+                }
             }
         }
     }
@@ -154,6 +158,25 @@ impl Parser {
         })
     }
 
+    fn forstmt(&mut self) -> Result<Stmt, ParserError> {
+        self.err_on_eof()?;
+        let var = self.next();
+        if let TokenType::Ident(_) = &var.ty {
+            self.err_on_eof()?;
+            let x = self.next();
+            if x.ty != TokenType::Colon {
+                return Err(self.mk_error("Expected colon"))
+            }
+            self.err_on_eof()?;
+            let expr = self.assignment()?;
+            self.err_on_eof()?;
+            let stmt = self.statement()?;
+            Ok(Stmt::For{ var, expr, stmt: Box::new(stmt) })
+        } else {
+            Err(self.mk_error("Expected identifier after for"))
+        }
+    }
+
     fn block(&mut self) -> Result<Stmt, ParserError> {
         let mut stmts = vec![];
         while !self.at_end() && self.peek().ty != TokenType::RBrace {
@@ -263,7 +286,7 @@ impl Parser {
         if matches!(next.ty, 
             TokenType::True | TokenType::False | TokenType::Nil 
             | TokenType::Int(_) | TokenType::Float(_) | TokenType::ImFloat(_)
-            | TokenType::String(_) 
+            | TokenType::String(_) | TokenType::Char(_)
         ) {
             Ok(Expr::Literal { value: next })
         } else if let TokenType::Ident(..) = next.ty {

src/token.rs

@@ -18,7 +18,7 @@ impl fmt::Debug for Token {
 
 #[derive(Clone, Debug, PartialEq)]
 pub enum TokenType {
-    Int(i64), Float(f64), ImFloat(f64), String(Rc<str>),
+    Int(i64), Float(f64), ImFloat(f64), String(Rc<str>), Char(char),
     Ident(Rc<str>),
 
     Plus, Minus, Star, Slash, Percent, DoubleSlash, Caret,
@@ -29,7 +29,7 @@ pub enum TokenType {
 
     Arrow, PipeColon, PipePoint, PipeQuestion, PipeAmper,
 
-    Comma, Semicolon, 
+    Comma, Semicolon, Colon, 
 
     LParen, RParen, LBrack, RBrack, LBrace, RBrace,
 

src/value.rs

@@ -1,4 +1,4 @@
-use std::{rc::Rc, collections::HashMap, ops::*};
+use std::{rc::Rc, collections::HashMap, ops::*, ascii::AsciiExt};
 
 use num_traits::Zero;
 
@@ -54,6 +54,7 @@ pub enum Value {
     Nil,
     Int(i64), Float(f64), Complex(Complex), Rational(Rational),
     Bool(bool), 
+    Char(char),
     String(Rc<str>), 
     List(Rc<Vec<Value>>), Map(Rc<HashMap<Value,Value>>),
 }
@@ -72,6 +73,16 @@ impl Value {
             _ => true
         }
     }
+
+    pub fn iter(&self) -> Result<Box<dyn Iterator<Item=Value> + '_>, ()> {
+        match self {
+            Value::String(s) 
+                => Ok(Box::new(s.chars()
+                    .map(|c| Value::Char(c)))),
+            Value::List(l) => Ok(Box::new(l.iter().cloned())),
+            _ => Err(())
+        }
+    }
 }
 
 
@@ -81,11 +92,23 @@ value_from!(Complex, Complex);
 value_from!(Rational, Rational);
 value_from!(Bool, bool);
 value_from!(String, String Rc<str>);
+value_from!(Char, char);
 value_from!(List, Vec<Value>);
 value_from!(Map, HashMap<Value,Value>);
 
 impl_numeric_op!(Add, add, {
     (String(a), String(b)) => Ok(((**a).to_owned() + b).into()),
+    (String(a), Char(c)) => {
+        let mut s = (**a).to_owned();
+        s.push(*c);
+        Ok(s.into())
+    },
+    (Char(c), String(a)) => Ok((c.to_string() + a).into()),
+    (Char(c1), Char(c2)) => {
+        let mut s = c1.to_string();
+        s.push(*c2);
+        Ok(s.into())
+    }
     (List(a), List(b)) => {
         let mut a = (**a).clone();
         a.append(&mut (**b).clone());

tests/code.cxpr

@@ -1,7 +1,4 @@
-if false {
-
-} elif true {
-
-} else {
 
+for c: "asdfghjkl" {
+    let b = 'q' + c;
 }