dnlmlr/nek-lang
dnlmlr/nek-lang
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Implement multi statement code

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- Add statements
- Add mandatory semicolons after statements
This commit is contained in:
Kai-Philipp Nosper 2022-01-29 23:18:15 +01:00
parent 23d336d63e
commit 35fbae8ab9
5 changed files with 108 additions and 48 deletions
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8
README.md
View File

@ -36,6 +36,7 @@
- [x] Variables
- [x] Declaration
- [x] Assignment
- [x] Statements with semicolon & Multiline programs
- [ ] Control flow
- [ ] While loop `while X { ... }`
- [ ] If else statement `if X { ... } else { ... }`
@ -50,7 +51,6 @@
## Grammar
### Expressions
```
expr_primary = LITERAL | IDENT | "(" expr ")" | "-" expr_primary | "~" expr_primary
expr_mul = expr_primary (("*" | "/" | "%") expr_primary)*
@ -63,3 +63,9 @@ expr_bxor = expr_band ("^" expr_band)*
expr_bor = expr_bxor ("|" expr_bxor)*
expr = expr_bor
```
### Statements
```
stmt_expr = expr ";"
stmt = stmt_expr
```

42
src/interpreter.rs
View File

@ -1,6 +1,6 @@
use std::collections::HashMap;
use crate::parser::{Ast, BinOpType, UnOpType};
use crate::parser::{Expression, BinOpType, UnOpType, Ast, Statement};
#[derive(Debug, PartialEq, Eq, Clone)]
pub enum Value {
@ -20,17 +20,23 @@ impl Interpreter {
}
pub fn run(&mut self, prog: Ast) {
let result = self.resolve_expr(prog);
for stmt in prog.prog {
match stmt {
Statement::Expr(expr) => {
let result = self.resolve_expr(expr);
println!("Result = {:?}", result);
}
}
println!("Result = {:?}", result);
}
}
fn resolve_expr(&mut self, expr: Ast) -> Value {
fn resolve_expr(&mut self, expr: Expression) -> Value {
match expr {
Ast::I64(val) => Value::I64(val),
Ast::BinOp(bo, lhs, rhs) => self.resolve_binop(bo, *lhs, *rhs),
Ast::UnOp(uo, operand) => self.resolve_unop(uo, *operand),
Ast::Var(name) => self.resolve_var(name),
Expression::I64(val) => Value::I64(val),
Expression::BinOp(bo, lhs, rhs) => self.resolve_binop(bo, *lhs, *rhs),
Expression::UnOp(uo, operand) => self.resolve_unop(uo, *operand),
Expression::Var(name) => self.resolve_var(name),
}
}
@ -41,7 +47,7 @@ impl Interpreter {
}
}
fn resolve_unop(&mut self, uo: UnOpType, operand: Ast) -> Value {
fn resolve_unop(&mut self, uo: UnOpType, operand: Expression) -> Value {
let operand = self.resolve_expr(operand);
match (operand, uo) {
@ -51,15 +57,15 @@ impl Interpreter {
}
}
fn resolve_binop(&mut self, bo: BinOpType, lhs: Ast, rhs: Ast) -> Value {
fn resolve_binop(&mut self, bo: BinOpType, lhs: Expression, rhs: Expression) -> Value {
let rhs = self.resolve_expr(rhs);
match (&bo, &lhs) {
(BinOpType::Declare, Ast::Var(name)) => {
(BinOpType::Declare, Expression::Var(name)) => {
self.vartable.insert(name.clone(), rhs.clone());
return rhs;
}
(BinOpType::Assign, Ast::Var(name)) => {
(BinOpType::Assign, Expression::Var(name)) => {
match self.vartable.get_mut(name) {
Some(val) => *val = rhs.clone(),
None => panic!("Runtime Error: Trying to assign value to undeclared variable"),
@ -100,21 +106,21 @@ impl Interpreter {
#[cfg(test)]
mod test {
use super::{Interpreter, Value};
use crate::parser::{Ast, BinOpType};
use crate::parser::{Expression, BinOpType};
#[test]
fn test_interpreter_expr() {
// Expression: 1 + 2 * 3 + 4
// With precedence: (1 + (2 * 3)) + 4
let ast = Ast::BinOp(
let ast = Expression::BinOp(
BinOpType::Add,
Ast::BinOp(
Expression::BinOp(
BinOpType::Add,
Ast::I64(1).into(),
Ast::BinOp(BinOpType::Mul, Ast::I64(2).into(), Ast::I64(3).into()).into(),
Expression::I64(1).into(),
Expression::BinOp(BinOpType::Mul, Expression::I64(2).into(), Expression::I64(3).into()).into(),
)
.into(),
Ast::I64(4).into(),
Expression::I64(4).into(),
);
let expected = Value::I64(11);

6
src/lexer.rs
View File

@ -73,6 +73,9 @@ pub enum Token {
/// Equal Sign (=)
Equ,
/// Semicolon (;)
Semicolon,
/// End of file
EoF,
}
@ -93,7 +96,7 @@ impl<'a> Lexer<'a> {
loop {
match self.next() {
// Skip whitespace
' ' | '\t' => (),
' ' | '\t' | '\n' | '\r' => (),
// Stop lexing at EOF
'\0' => break,
@ -127,6 +130,7 @@ impl<'a> Lexer<'a> {
tokens.push(Token::LArrow);
}
';' => tokens.push(Token::Semicolon),
'+' => tokens.push(Token::Add),
'-' => tokens.push(Token::Sub),
'*' => tokens.push(Token::Mul),

20
src/main.rs
View File

@ -7,15 +7,19 @@ fn main() {
let mut interpreter = Interpreter::new();
let mut code = String::new();
// let mut code = String::new();
let code = "
a <- 5;
a * 2;
";
loop {
print!(">> ");
std::io::stdout().flush().unwrap();
// loop {
// print!(">> ");
// std::io::stdout().flush().unwrap();
code.clear();
std::io::stdin().read_line(&mut code).unwrap();
let code = code.trim();
// code.clear();
// std::io::stdin().read_line(&mut code).unwrap();
// let code = code.trim();
let tokens = lex(&code);
@ -26,6 +30,6 @@ fn main() {
println!("Ast: {:#?}\n", ast);
interpreter.run(ast);
}
// }
}

80
src/parser.rs
View File

@ -70,15 +70,25 @@ pub enum UnOpType {
}
#[derive(Debug, PartialEq, Eq, Clone)]
pub enum Ast {
pub enum Expression {
/// Integer literal (64-bit)
I64(i64),
/// Variable
Var(String),
/// Binary operation. Consists of type, left hand side and right hand side
BinOp(BinOpType, Box<Ast>, Box<Ast>),
BinOp(BinOpType, Box<Expression>, Box<Expression>),
/// Unary operation. Consists of type and operand
UnOp(UnOpType, Box<Ast>),
UnOp(UnOpType, Box<Expression>),
}
#[derive(Debug, PartialEq, Eq, Clone)]
pub enum Statement {
Expr(Expression),
}
#[derive(Debug, PartialEq, Eq, Clone)]
pub struct Ast {
pub prog: Vec<Statement>
}
struct Parser<T: Iterator<Item = Token>> {
@ -93,16 +103,44 @@ impl<T: Iterator<Item = Token>> Parser<T> {
}
fn parse(&mut self) -> Ast {
self.parse_expr()
let mut prog = Vec::new();
loop {
match self.peek() {
Token::Semicolon => {
self.next();
}
Token::EoF => break,
// By default try to lex a statement
_ => {
prog.push(self.parse_stmt())
}
}
}
Ast { prog }
}
fn parse_expr(&mut self) -> Ast {
fn parse_stmt(&mut self) -> Statement {
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::Expr(expr)
}
fn parse_expr(&mut self) -> Expression {
let lhs = self.parse_primary();
self.parse_expr_precedence(lhs, 0)
}
/// Parse binary expressions with a precedence equal to or higher than min_prec
fn parse_expr_precedence(&mut self, mut lhs: Ast, min_prec: u8) -> Ast {
fn parse_expr_precedence(&mut self, mut lhs: Expression, min_prec: u8) -> Expression {
while let Some(binop) = &self.peek().try_to_binop() {
// Stop if the next operator has a lower binding power
if !(binop.precedence() >= min_prec) {
@ -123,19 +161,19 @@ impl<T: Iterator<Item = Token>> Parser<T> {
rhs = self.parse_expr_precedence(rhs, binop.precedence() + 1);
}
lhs = Ast::BinOp(binop, lhs.into(), rhs.into());
lhs = Expression::BinOp(binop, lhs.into(), rhs.into());
}
lhs
}
/// Parse a primary expression (for now only number)
fn parse_primary(&mut self) -> Ast {
fn parse_primary(&mut self) -> Expression {
match self.next() {
// Literal i64
Token::I64(val) => Ast::I64(val),
Token::I64(val) => Expression::I64(val),
Token::Ident(name) => Ast::Var(name),
Token::Ident(name) => Expression::Var(name),
// Parentheses grouping
Token::LParen => {
@ -152,12 +190,12 @@ impl<T: Iterator<Item = Token>> Parser<T> {
// Unary negation
Token::Sub => {
let operand = self.parse_primary();
Ast::UnOp(UnOpType::Negate, operand.into())
Expression::UnOp(UnOpType::Negate, operand.into())
}
Token::Tilde => {
let operand = self.parse_primary();
Ast::UnOp(UnOpType::BNot, operand.into())
Expression::UnOp(UnOpType::BNot, operand.into())
}
tok => panic!("Error parsing primary expr: Unexpected Token '{:?}'", tok),
@ -206,8 +244,8 @@ impl BinOpType {
#[cfg(test)]
mod tests {
use super::{parse, Ast, BinOpType};
use crate::lexer::Token;
use super::{parse, Expression, BinOpType};
use crate::{lexer::Token, parser::{Statement, Ast}};
#[test]
fn test_parser() {
@ -223,16 +261,18 @@ mod tests {
Token::I64(4),
];
let expected = Ast::BinOp(
let expected = Statement::Expr(Expression::BinOp(
BinOpType::Sub,
Ast::BinOp(
Expression::BinOp(
BinOpType::Add,
Ast::I64(1).into(),
Ast::BinOp(BinOpType::Mul, Ast::I64(2).into(), Ast::I64(3).into()).into(),
Expression::I64(1).into(),
Expression::BinOp(BinOpType::Mul, Expression::I64(2).into(), Expression::I64(3).into()).into(),
)
.into(),
Ast::I64(4).into(),
);
Expression::I64(4).into(),
));
let expected = Ast { prog: vec![expected] };
let actual = parse(tokens);
assert_eq!(expected, actual);