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#[macro_use]
extern crate pest_derive;
#[macro_use]
extern crate pest;
mod parser {
#[derive(Parser)]
#[grammar = "grammar.pest"]
pub struct Parser;
}
mod ast {
use super::parser::Rule;
pub fn from_parse_tree(parse_tree: &mut pest::iterators::Pairs<Rule>) -> Program {
let root = parse_tree.next().unwrap();
match root.as_rule() {
Rule::program => {
let statements_with_eoi: Vec<pest::iterators::Pair<Rule>> =
root.into_inner().collect();
let statements_split = statements_with_eoi.split_last().unwrap();
let statements = statements_split.1.to_vec();
statements
.iter()
.map(|s| Statement::from_pair(s.clone()))
.collect()
}
_ => panic!("[ast] first Pair is not a program"),
}
}
pub type Program = Vec<Statement>;
#[derive(Debug)]
pub enum Statement {
Definition {
symbol: Symbol,
expression: Expression,
},
Expression(Expression),
}
impl Statement {
fn from_pair(pair: pest::iterators::Pair<Rule>) -> Statement {
let def_or_expr = pair.into_inner().next().unwrap();
fn definition_from_pair(pair: pest::iterators::Pair<Rule>) -> Statement {
let mut inner = pair.into_inner();
let symbol = inner.next().unwrap().as_span().as_str();
let expression = inner.next().unwrap();
let expression_inners: Vec<ExpressionInner> = expression
.into_inner()
.map(ExpressionInner::from_pair)
.collect();
Statement::Definition {
symbol: String::from(symbol),
expression: expression_inners,
}
}
match def_or_expr.as_rule() {
Rule::definition => definition_from_pair(def_or_expr),
Rule::expression => {
let expression_inners: Vec<ExpressionInner> = def_or_expr
.into_inner()
.map(ExpressionInner::from_pair)
.collect();
Statement::Expression(expression_inners)
}
rule => panic!("[ast] can't make a statement from {:#?}", rule),
}
}
}
#[derive(Debug)]
pub enum ExpressionInner {
Symbol(Symbol),
IntegerLiteral(IntegerLiteral),
StringLiteral(StringLiteral),
Expression(Expression),
}
impl ExpressionInner {
fn from_pair(pair: pest::iterators::Pair<Rule>) -> ExpressionInner {
// println!("ExpressionInner::from_pair pair: {:#?}", pair);
match pair.as_rule() {
Rule::symbol => ExpressionInner::Symbol(string_from_pair(pair)),
Rule::integer_literal => ExpressionInner::IntegerLiteral(integer_from_pair(pair)),
Rule::string_literal => {
let s_with_quotes = string_from_pair(pair);
let mut chars = s_with_quotes.chars();
chars.next();
chars.next_back();
let s = chars.as_str();
ExpressionInner::StringLiteral(String::from(s))
}
Rule::expression => {
let expression_inners: Vec<ExpressionInner> =
pair.into_inner().map(ExpressionInner::from_pair).collect();
ExpressionInner::Expression(expression_inners)
}
rule => panic!("[ast] can't make an expression element from {:#?}", rule),
}
}
}
pub type Expression = Vec<ExpressionInner>;
pub type IntegerLiteral = i64;
fn integer_from_pair(pair: pest::iterators::Pair<Rule>) -> i64 {
let s = pair.as_span().as_str();
s.parse().unwrap()
}
pub type StringLiteral = String;
fn string_from_pair(pair: pest::iterators::Pair<Rule>) -> String {
String::from(pair.as_span().as_str())
}
pub type Symbol = String;
}
mod runtime {
use super::ast;
use std::collections::HashMap;
#[derive(Debug, Clone)]
pub enum Value {
Integer(i64),
String(String),
}
fn try_evaluate_builtin(symbol: &ast::Symbol) -> Option<Value> {
match symbol.as_str() {
"int.zero" => Some(Value::Integer(0)),
_ => None,
}
}
fn evaluate_expr(symbol_table: &HashMap<String, Value>, expression: &ast::Expression) -> Value {
// println!("[runtime] evaluating expression");
let head = &expression[0];
let tail = &expression[1..];
let arity = tail.len();
match head {
ast::ExpressionInner::IntegerLiteral(value) => match arity {
0 => Value::Integer(*value),
_ => panic!("[runtime] cannot apply integer: {}", value),
},
ast::ExpressionInner::StringLiteral(value) => match arity {
0 => Value::String(value.clone()),
_ => panic!("[runtime] cannot apply string: {}", value),
},
ast::ExpressionInner::Symbol(value) => {
let builtin_value = try_evaluate_builtin(value);
if builtin_value.is_some() {
return builtin_value.unwrap();
}
let table_lookup_value = symbol_table.get(value);
if table_lookup_value.is_some() {
return table_lookup_value.unwrap().clone();
}
Value::String(String::from("dummy value"))
}
ast::ExpressionInner::Expression(expression) => evaluate_expr(symbol_table, expression),
}
}
pub fn evaluate(program: &ast::Program) {
let mut symbol_table: HashMap<String, Value> = HashMap::new();
for statement in program {
match statement {
ast::Statement::Definition { symbol, expression } => {
println!("[runtime] defining symbol: {:#?}", symbol);
let value = evaluate_expr(&symbol_table, expression);
symbol_table.insert(symbol.clone(), value);
}
ast::Statement::Expression(expression) => {
println!("[runtime] evaluating free-standing expression");
let value = evaluate_expr(&symbol_table, expression);
println!("Result: {:#?}", value);
}
}
}
println!(
"[runtime] evaluation done, symbol_table state dump: {:#?}",
symbol_table
);
}
}
fn main() {
use ast::Program;
use pest::Parser;
use std::fs;
let unparsed_file = fs::read_to_string("samples/sample1.code").expect("cannot read file");
let parse_tree_result = parser::Parser::parse(parser::Rule::program, &unparsed_file);
if parse_tree_result.is_err() {
println!("{}", parse_tree_result.unwrap_err());
return;
}
let mut parse_tree = parse_tree_result.unwrap();
// println!("parse tree = {:#?}", parse_tree);
let syntax_tree: Program = ast::from_parse_tree(&mut parse_tree);
println!("syntax tree = {:#?}", syntax_tree);
runtime::evaluate(&syntax_tree);
}
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