schala/schala-lang/language/src/eval.rs
2018-11-06 01:19:16 -08:00

737 lines
22 KiB
Rust

use std::cell::RefCell;
use std::rc::Rc;
use std::fmt::Write;
use std::io;
use itertools::Itertools;
use util::ScopeStack;
use reduced_ast::{BoundVars, ReducedAST, Stmt, Expr, Lit, Func, Alternative, Subpattern};
use symbol_table::{SymbolSpec, Symbol, SymbolTable};
pub struct State<'a> {
values: ScopeStack<'a, Rc<String>, ValueEntry>,
symbol_table_handle: Rc<RefCell<SymbolTable>>,
}
macro_rules! builtin_binding {
($name:expr, $values:expr) => {
$values.insert(Rc::new(format!($name)), ValueEntry::Binding { constant: true, val: Node::Expr(Expr::Func(Func::BuiltIn(Rc::new(format!($name))))) });
}
}
impl<'a> State<'a> {
pub fn new(symbol_table_handle: Rc<RefCell<SymbolTable>>) -> State<'a> {
let mut values = ScopeStack::new(Some(format!("global")));
builtin_binding!("print", values);
builtin_binding!("println", values);
builtin_binding!("getline", values);
State { values, symbol_table_handle }
}
pub fn debug_print(&self) -> String {
format!("Values: {:?}", self.values)
}
fn new_frame(&'a self, items: &'a Vec<Node>, bound_vars: &BoundVars) -> State<'a> {
let mut inner_state = State {
values: self.values.new_scope(None),
symbol_table_handle: self.symbol_table_handle.clone(),
};
for (bound_var, val) in bound_vars.iter().zip(items.iter()) {
if let Some(bv) = bound_var.as_ref() {
inner_state.values.insert(bv.clone(), ValueEntry::Binding { constant: true, val: val.clone() });
}
}
inner_state
}
}
#[derive(Debug, Clone)]
enum Node {
Expr(Expr),
PrimObject {
name: Rc<String>,
tag: usize,
items: Vec<Node>,
},
PrimTuple {
items: Vec<Node>
}
}
fn paren_wrapped_vec(terms: impl Iterator<Item=String>) -> String {
let mut buf = String::new();
write!(buf, "(").unwrap();
for term in terms.map(|e| Some(e)).intersperse(None) {
match term {
Some(e) => write!(buf, "{}", e).unwrap(),
None => write!(buf, ", ").unwrap(),
};
}
write!(buf, ")").unwrap();
buf
}
impl Node {
fn to_repl(&self) -> String {
match self {
Node::Expr(e) => e.to_repl(),
Node::PrimObject { name, items, .. } if items.len() == 0 => format!("{}", name),
Node::PrimObject { name, items, .. } => format!("{}{}", name, paren_wrapped_vec(items.iter().map(|x| x.to_repl()))),
Node::PrimTuple { items } => format!("{}", paren_wrapped_vec(items.iter().map(|x| x.to_repl()))),
}
}
fn is_true(&self) -> bool {
match self {
Node::Expr(Expr::Lit(::reduced_ast::Lit::Bool(true))) => true,
_ => false,
}
}
}
#[derive(Debug)]
enum ValueEntry {
Binding {
constant: bool,
val: /*FullyEvaluatedExpr*/ Node, //TODO make this use a subtype to represent fully evaluatedness
}
}
type EvalResult<T> = Result<T, String>;
impl Expr {
fn to_node(self) -> Node {
Node::Expr(self)
}
fn to_repl(&self) -> String {
use self::Lit::*;
use self::Func::*;
match self {
Expr::Lit(ref l) => match l {
Nat(n) => format!("{}", n),
Int(i) => format!("{}", i),
Float(f) => format!("{}", f),
Bool(b) => format!("{}", b),
StringLit(s) => format!("\"{}\"", s),
},
Expr::Func(f) => match f {
BuiltIn(name) => format!("<built-in function '{}'>", name),
UserDefined { name: None, .. } => format!("<function>"),
UserDefined { name: Some(name), .. } => format!("<function '{}'>", name),
},
Expr::Constructor {
type_name: _, name, arity, ..
} => if *arity == 0 {
format!("{}", name)
} else {
format!("<data constructor '{}'>", name)
},
Expr::Tuple(exprs) => paren_wrapped_vec(exprs.iter().map(|x| x.to_repl())),
_ => format!("{:?}", self),
}
}
fn replace_conditional_target_sigil(self, replacement: &Expr) -> Expr {
use self::Expr::*;
match self {
ConditionalTargetSigilValue => replacement.clone(),
Unit | Lit(_) | Func(_) | Val(_) | Constructor { .. } |
CaseMatch { .. } | UnimplementedSigilValue => self,
Tuple(exprs) => Tuple(exprs.into_iter().map(|e| e.replace_conditional_target_sigil(replacement)).collect()),
Call { f, args } => {
let new_args = args.into_iter().map(|e| e.replace_conditional_target_sigil(replacement)).collect();
Call { f, args: new_args }
},
Conditional { .. } => panic!("Dunno if I need this, but if so implement"),
Assign { .. } => panic!("I'm pretty sure I don't need this"),
}
}
}
impl<'a> State<'a> {
pub fn evaluate(&mut self, ast: ReducedAST, repl: bool) -> Vec<Result<String, String>> {
let mut acc = vec![];
// handle prebindings
for statement in ast.0.iter() {
self.prebinding(statement);
}
for statement in ast.0 {
match self.statement(statement) {
Ok(Some(ref output)) if repl => acc.push(Ok(output.to_repl())),
Ok(_) => (),
Err(error) => {
acc.push(Err(format!("Runtime error: {}", error)));
return acc;
},
}
}
acc
}
fn prebinding(&mut self, stmt: &Stmt) {
match stmt {
Stmt::PreBinding { name, func } => {
let v_entry = ValueEntry::Binding { constant: true, val: Node::Expr(Expr::Func(func.clone())) };
self.values.insert(name.clone(), v_entry);
},
Stmt::Expr(_expr) => {
//TODO have this support things like nested function defs
},
_ => ()
}
}
fn statement(&mut self, stmt: Stmt) -> EvalResult<Option<Node>> {
match stmt {
Stmt::Binding { name, constant, expr } => {
let val = self.expression(Node::Expr(expr))?;
self.values.insert(name.clone(), ValueEntry::Binding { constant, val });
Ok(None)
},
Stmt::Expr(expr) => Ok(Some(self.expression(expr.to_node())?)),
Stmt::PreBinding {..} | Stmt::Noop => Ok(None),
}
}
fn block(&mut self, stmts: Vec<Stmt>) -> EvalResult<Node> {
let mut ret = None;
for stmt in stmts {
ret = self.statement(stmt)?;
}
Ok(ret.unwrap_or(Node::Expr(Expr::Unit)))
}
fn expression(&mut self, node: Node) -> EvalResult<Node> {
use self::Expr::*;
match node {
t @ Node::PrimTuple { .. } => Ok(t),
obj @ Node::PrimObject { .. } => Ok(obj),
Node::Expr(expr) => match expr {
literal @ Lit(_) => Ok(Node::Expr(literal)),
Call { box f, args } => self.call_expression(f, args),
Val(v) => self.value(v),
Constructor { arity, ref name, tag, .. } if arity == 0 => Ok(Node::PrimObject { name: name.clone(), tag, items: vec![] }),
constructor @ Constructor { .. } => Ok(Node::Expr(constructor)),
func @ Func(_) => Ok(Node::Expr(func)),
Tuple(exprs) => {
let nodes = exprs.into_iter().map(|expr| self.expression(Node::Expr(expr))).collect::<Result<Vec<Node>,_>>()?;
Ok(Node::PrimTuple { items: nodes })
},
Conditional { box cond, then_clause, else_clause } => self.conditional(cond, then_clause, else_clause),
Assign { box val, box expr } => self.assign_expression(val, expr),
Unit => Ok(Node::Expr(Unit)),
CaseMatch { box cond, alternatives } => self.case_match_expression(cond, alternatives),
ConditionalTargetSigilValue => Ok(Node::Expr(ConditionalTargetSigilValue)),
UnimplementedSigilValue => Err(format!("Sigil value eval not implemented")),
}
}
}
fn call_expression(&mut self, f: Expr, args: Vec<Expr>) -> EvalResult<Node> {
use self::Expr::*;
match self.expression(Node::Expr(f))? {
Node::Expr(Constructor { type_name, name, tag, arity }) => self.apply_data_constructor(type_name, name, tag, arity, args),
Node::Expr(Func(f)) => self.apply_function(f, args),
other => return Err(format!("Tried to call {:?} which is not a function or data constructor", other)),
}
}
fn apply_data_constructor(&mut self, _type_name: Rc<String>, name: Rc<String>, tag: usize, arity: usize, args: Vec<Expr>) -> EvalResult<Node> {
if arity != args.len() {
return Err(format!("Data constructor {} requires {} args", name, arity));
}
let evaled_args = args.into_iter().map(|expr| self.expression(Node::Expr(expr))).collect::<Result<Vec<Node>,_>>()?;
//let evaled_args = vec![];
Ok(Node::PrimObject {
name: name.clone(),
items: evaled_args,
tag
})
}
fn apply_function(&mut self, f: Func, args: Vec<Expr>) -> EvalResult<Node> {
match f {
Func::BuiltIn(sigil) => Ok(Node::Expr(self.apply_builtin(sigil, args)?)),
Func::UserDefined { params, body, name } => {
if params.len() != args.len() {
return Err(format!("calling a {}-argument function with {} args", params.len(), args.len()))
}
let mut func_state = State {
values: self.values.new_scope(name.map(|n| format!("{}", n))),
symbol_table_handle: self.symbol_table_handle.clone(),
};
for (param, val) in params.into_iter().zip(args.into_iter()) {
let val = func_state.expression(Node::Expr(val))?;
func_state.values.insert(param, ValueEntry::Binding { constant: true, val });
}
// TODO figure out function return semantics
func_state.block(body)
}
}
}
fn apply_builtin(&mut self, name: Rc<String>, args: Vec<Expr>) -> EvalResult<Expr> {
use self::Expr::*;
use self::Lit::*;
let evaled_args: Result<Vec<Expr>, String> = args.into_iter().map(|arg| {
match self.expression(Node::Expr(arg)) {
Ok(Node::Expr(e)) => Ok(e),
Ok(Node::PrimTuple { .. }) => Err(format!("Trying to apply a builtin to a tuple")),
Ok(Node::PrimObject { .. }) => Err(format!("Trying to apply a builtin to a primitive object")),
Err(e) => Err(e)
}
}).collect();
let evaled_args = evaled_args?;
Ok(match (name.as_str(), evaled_args.as_slice()) {
/* binops */
("+", &[Lit(Nat(l)), Lit(Nat(r))]) => Lit(Nat(l + r)),
("++", &[Lit(StringLit(ref s1)), Lit(StringLit(ref s2))]) => Lit(StringLit(Rc::new(format!("{}{}", s1, s2)))),
("-", &[Lit(Nat(l)), Lit(Nat(r))]) => Lit(Nat(l - r)),
("*", &[Lit(Nat(l)), Lit(Nat(r))]) => Lit(Nat(l * r)),
("/", &[Lit(Nat(l)), Lit(Nat(r))]) => Lit(Float((l as f64)/ (r as f64))),
("//", &[Lit(Nat(l)), Lit(Nat(r))]) => if r == 0 {
return Err(format!("divide by zero"));
} else {
Lit(Nat(l / r))
},
("%", &[Lit(Nat(l)), Lit(Nat(r))]) => Lit(Nat(l % r)),
("^", &[Lit(Nat(l)), Lit(Nat(r))]) => Lit(Nat(l ^ r)),
("&", &[Lit(Nat(l)), Lit(Nat(r))]) => Lit(Nat(l & r)),
("|", &[Lit(Nat(l)), Lit(Nat(r))]) => Lit(Nat(l | r)),
/* comparisons */
("==", &[Lit(Nat(l)), Lit(Nat(r))]) => Lit(Bool(l == r)),
("==", &[Lit(Int(l)), Lit(Int(r))]) => Lit(Bool(l == r)),
("==", &[Lit(Float(l)), Lit(Float(r))]) => Lit(Bool(l == r)),
("==", &[Lit(Bool(l)), Lit(Bool(r))]) => Lit(Bool(l == r)),
("==", &[Lit(StringLit(ref l)), Lit(StringLit(ref r))]) => Lit(Bool(l == r)),
("<", &[Lit(Nat(l)), Lit(Nat(r))]) => Lit(Bool(l < r)),
("<", &[Lit(Int(l)), Lit(Int(r))]) => Lit(Bool(l < r)),
("<", &[Lit(Float(l)), Lit(Float(r))]) => Lit(Bool(l < r)),
("<=", &[Lit(Nat(l)), Lit(Nat(r))]) => Lit(Bool(l <= r)),
("<=", &[Lit(Int(l)), Lit(Int(r))]) => Lit(Bool(l <= r)),
("<=", &[Lit(Float(l)), Lit(Float(r))]) => Lit(Bool(l <= r)),
(">", &[Lit(Nat(l)), Lit(Nat(r))]) => Lit(Bool(l > r)),
(">", &[Lit(Int(l)), Lit(Int(r))]) => Lit(Bool(l > r)),
(">", &[Lit(Float(l)), Lit(Float(r))]) => Lit(Bool(l > r)),
(">=", &[Lit(Nat(l)), Lit(Nat(r))]) => Lit(Bool(l >= r)),
(">=", &[Lit(Int(l)), Lit(Int(r))]) => Lit(Bool(l >= r)),
(">=", &[Lit(Float(l)), Lit(Float(r))]) => Lit(Bool(l >= r)),
/* prefix ops */
("!", &[Lit(Bool(true))]) => Lit(Bool(false)),
("!", &[Lit(Bool(false))]) => Lit(Bool(true)),
("-", &[Lit(Nat(n))]) => Lit(Int(-1*(n as i64))),
("-", &[Lit(Int(n))]) => Lit(Int(-1*(n as i64))),
("+", &[Lit(Int(n))]) => Lit(Int(n)),
("+", &[Lit(Nat(n))]) => Lit(Nat(n)),
/* builtin functions */
("print", &[ref anything]) => {
print!("{}", anything.to_repl());
Expr::Unit
},
("println", &[ref anything]) => {
println!("{}", anything.to_repl());
Expr::Unit
},
("getline", &[]) => {
let mut buf = String::new();
io::stdin().read_line(&mut buf).expect("Error readling line in 'getline'");
Lit(StringLit(Rc::new(buf.trim().to_string())))
},
(x, args) => return Err(format!("bad or unimplemented builtin {:?} | {:?}", x, args)),
})
}
fn conditional(&mut self, cond: Expr, then_clause: Vec<Stmt>, else_clause: Vec<Stmt>) -> EvalResult<Node> {
let cond = self.expression(Node::Expr(cond))?;
Ok(match cond {
Node::Expr(Expr::Lit(Lit::Bool(true))) => self.block(then_clause)?,
Node::Expr(Expr::Lit(Lit::Bool(false))) => self.block(else_clause)?,
_ => return Err(format!("Conditional with non-boolean condition"))
})
}
fn assign_expression(&mut self, val: Expr, expr: Expr) -> EvalResult<Node> {
let name = match val {
Expr::Val(name) => name,
_ => return Err(format!("Trying to assign to a non-value")),
};
let constant = match self.values.lookup(&name) {
None => return Err(format!("Constant {} is undefined", name)),
Some(ValueEntry::Binding { constant, .. }) => constant.clone(),
};
if constant {
return Err(format!("trying to update {}, a non-mutable binding", name));
}
let val = self.expression(Node::Expr(expr))?;
self.values.insert(name.clone(), ValueEntry::Binding { constant: false, val });
Ok(Node::Expr(Expr::Unit))
}
fn guard_passes(&mut self, guard: &Option<Expr>, cond: &Node) -> EvalResult<bool> {
if let Some(ref guard_expr) = guard {
let guard_expr = match cond {
Node::Expr(ref e) => guard_expr.clone().replace_conditional_target_sigil(e),
_ => guard_expr.clone()
};
Ok(self.expression(guard_expr.to_node())?.is_true())
} else {
Ok(true)
}
}
fn case_match_expression(&mut self, cond: Expr, alternatives: Vec<Alternative>) -> EvalResult<Node> {
//TODO need to handle recursive subpatterns
let all_subpatterns_pass = |state: &mut State, subpatterns: &Vec<Option<Subpattern>>, items: &Vec<Node>| -> EvalResult<bool> {
if subpatterns.len() == 0 {
return Ok(true)
}
if items.len() != subpatterns.len() {
return Err(format!("Subpattern length isn't correct items {} subpatterns {}", items.len(), subpatterns.len()));
}
for (maybe_subp, cond) in subpatterns.iter().zip(items.iter()) {
if let Some(subp) = maybe_subp {
if !state.guard_passes(&subp.guard, &cond)? {
return Ok(false)
}
}
}
Ok(true)
};
let cond = self.expression(Node::Expr(cond))?;
for alt in alternatives {
// no matter what type of condition we have, ignore alternative if the guard evaluates false
if !self.guard_passes(&alt.guard, &cond)? {
continue;
}
match cond {
Node::PrimObject { ref tag, ref items, .. } => {
if alt.tag.map(|t| t == *tag).unwrap_or(true) {
let mut inner_state = self.new_frame(items, &alt.bound_vars);
if all_subpatterns_pass(&mut inner_state, &alt.subpatterns, items)? {
return inner_state.block(alt.item);
} else {
continue;
}
}
},
Node::PrimTuple { ref items } => {
let mut inner_state = self.new_frame(items, &alt.bound_vars);
if all_subpatterns_pass(&mut inner_state, &alt.subpatterns, items)? {
return inner_state.block(alt.item);
} else {
continue;
}
},
Node::Expr(ref _e) => {
if let None = alt.tag {
return self.block(alt.item)
}
}
}
}
Err(format!("{:?} failed pattern match", cond))
}
fn value(&mut self, name: Rc<String>) -> EvalResult<Node> {
use self::ValueEntry::*;
use self::Func::*;
//TODO add a layer of indirection here to talk to the symbol table first, and only then look up
//in the values table
let symbol_table = self.symbol_table_handle.borrow();
let value = symbol_table.lookup_by_name(&name);
Ok(match value {
Some(Symbol { name, spec }) => match spec {
//TODO I'll need this type_name later to do a table lookup
SymbolSpec::DataConstructor { type_name: _type_name, type_args, .. } => {
if type_args.len() == 0 {
Node::PrimObject { name: name.clone(), tag: 0, items: vec![] }
} else {
return Err(format!("This data constructor thing not done"))
}
},
SymbolSpec::Func(_) => match self.values.lookup(&name) {
Some(Binding { val: Node::Expr(Expr::Func(UserDefined { name, params, body })), .. }) => {
Node::Expr(Expr::Func(UserDefined { name: name.clone(), params: params.clone(), body: body.clone() }))
},
_ => unreachable!(),
},
},
/* see if it's an ordinary variable TODO make variables go in symbol table */
None => match self.values.lookup(&name) {
Some(Binding { val, .. }) => val.clone(),
None => return Err(format!("Couldn't find value {}", name)),
}
})
}
}
#[cfg(test)]
mod eval_tests {
use std::cell::RefCell;
use std::rc::Rc;
use tokenizing::{Token, tokenize};
use ::parsing::ParseResult;
use ::ast::AST;
use symbol_table::SymbolTable;
use eval::State;
fn parse(tokens: Vec<Token>) -> ParseResult<AST> {
let mut parser = ::parsing::Parser::new(tokens);
parser.parse()
}
fn evaluate_all_outputs(input: &str) -> Vec<Result<String, String>> {
let symbol_table = Rc::new(RefCell::new(SymbolTable::new()));
let mut state = State::new(symbol_table);
let ast = parse(tokenize(input)).unwrap();
state.symbol_table_handle.borrow_mut().add_top_level_symbols(&ast).unwrap();
let reduced = ast.reduce(&state.symbol_table_handle.borrow());
let all_output = state.evaluate(reduced, true);
all_output
}
macro_rules! test_in_fresh_env {
($string:expr, $correct:expr) => {
{
let all_output = evaluate_all_outputs($string);
let ref output = all_output.last().unwrap();
assert_eq!(**output, Ok($correct.to_string()));
}
}
}
#[test]
fn test_basic_eval() {
test_in_fresh_env!("1 + 2", "3");
test_in_fresh_env!("let mut a = 1; a = 2", "Unit");
test_in_fresh_env!("let mut a = 1; a = 2; a", "2");
test_in_fresh_env!(r#"("a", 1 + 2)"#, r#"("a", 3)"#);
}
#[test]
fn function_eval() {
test_in_fresh_env!("fn oi(x) { x + 1 }; oi(4)", "5");
test_in_fresh_env!("fn oi(x) { x + 1 }; oi(1+2)", "4");
}
#[test]
fn scopes() {
let scope_ok = r#"
let a = 20
fn haha() {
let a = 10
a
}
haha()
"#;
test_in_fresh_env!(scope_ok, "10");
let scope_ok = r#"
let a = 20
fn haha() {
let a = 10
a
}
a
"#;
test_in_fresh_env!(scope_ok, "20");
}
#[test]
fn if_is_patterns() {
let source = r#"
type Option<T> = Some(T) | None
let x = Some(9); if x is Some(q) then { q } else { 0 }"#;
test_in_fresh_env!(source, "9");
let source = r#"
type Option<T> = Some(T) | None
let x = None; if x is Some(q) then { q } else { 0 }"#;
test_in_fresh_env!(source, "0");
}
#[test]
fn full_if_matching() {
let source = r#"
type Option<T> = Some(T) | None
let a = None
if a { is None -> 4, is Some(x) -> x }
"#;
test_in_fresh_env!(source, "4");
let source = r#"
type Option<T> = Some(T) | None
let a = Some(99)
if a { is None -> 4, is Some(x) -> x }
"#;
test_in_fresh_env!(source, "99");
let source = r#"
let a = 10
if a { is 10 -> "x", is 4 -> "y" }
"#;
test_in_fresh_env!(source, "\"x\"");
let source = r#"
let a = 10
if a { is 15 -> "x", is 10 -> "y" }
"#;
test_in_fresh_env!(source, "\"y\"");
}
#[test]
fn string_pattern() {
let source = r#"
let a = "foo"
if a { is "foo" -> "x", is _ -> "y" }
"#;
test_in_fresh_env!(source, "\"x\"");
}
#[test]
fn boolean_pattern() {
let source = r#"
let a = true
if a {
is true -> "x",
is false -> "y"
}
"#;
test_in_fresh_env!(source, "\"x\"");
}
#[test]
fn boolean_pattern_2() {
let source = r#"
let a = false
if a { is true -> "x", is false -> "y" }
"#;
test_in_fresh_env!(source, "\"y\"");
}
#[test]
fn ignore_pattern() {
let source = r#"
type Option<T> = Some(T) | None
if Some(10) {
is _ -> "hella"
}
"#;
test_in_fresh_env!(source, "\"hella\"");
}
#[test]
fn tuple_pattern() {
let source = r#"
if (1, 2) {
is (1, x) -> x,
is _ -> 99
}
"#;
test_in_fresh_env!(source, 2);
}
#[test]
fn tuple_pattern_2() {
let source = r#"
if (1, 2) {
is (10, x) -> x,
is (y, x) -> x + y
}
"#;
test_in_fresh_env!(source, 3);
}
#[test]
fn tuple_pattern_3() {
let source = r#"
if (1, 5) {
is (10, x) -> x,
is (1, x) -> x
}
"#;
test_in_fresh_env!(source, 5);
}
#[test]
fn tuple_pattern_4() {
let source = r#"
if (1, 5) {
is (10, x) -> x,
is (1, x) -> x,
}
"#;
test_in_fresh_env!(source, 5);
}
#[test]
fn prim_obj_pattern() {
let source = r#"
type Stuff = Mulch(Nat) | Jugs(Nat, String) | Mardok
let a = Mulch(20)
let b = Jugs(1, "haha")
let c = Mardok
let x = if a {
is Mulch(20) -> "x",
is _ -> "ERR"
}
let y = if b {
is Mulch(n) -> "ERR",
is Jugs(2, _) -> "ERR",
is Jugs(1, s) -> s,
is _ -> "ERR",
}
let z = if c {
is Jugs(_, _) -> "ERR",
is Mardok -> "NIGH",
is _ -> "ERR",
}
(x, y, z)
"#;
test_in_fresh_env!(source, r#"("x", "haha", "NIGH")"#);
}
#[test]
fn basic_lambda_syntax() {
let source = r#"
let q = \(x, y) { x * y }
let x = q(5,2)
let y = \(m, n, o) { m + n + o }(1,2,3)
(x, y)
"#;
test_in_fresh_env!(source, r"(10, 6)");
}
}