schala/schala-lang/language/src/eval.rs
2019-09-10 03:40:41 -07:00

503 lines
18 KiB
Rust

use std::cell::RefCell;
use std::rc::Rc;
use std::fmt::Write;
use std::io;
use itertools::Itertools;
use crate::util::ScopeStack;
use crate::reduced_ast::{BoundVars, ReducedAST, Stmt, Expr, Lit, Func, Alternative, Subpattern};
use crate::symbol_table::{SymbolSpec, Symbol, SymbolTable, ScopeSegment, ScopeSegmentKind, FullyQualifiedSymbolName};
use crate::builtin::Builtin;
mod test;
pub struct State<'a> {
values: ScopeStack<'a, Rc<String>, ValueEntry>,
symbol_table_handle: Rc<RefCell<SymbolTable>>,
}
impl<'a> State<'a> {
pub fn new(symbol_table_handle: Rc<RefCell<SymbolTable>>) -> State<'a> {
let values = ScopeStack::new(Some(format!("global")));
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, symbol_table: &SymbolTable) -> String {
match self {
Node::Expr(e) => e.to_repl(symbol_table),
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(symbol_table)))),
Node::PrimTuple { items } => format!("{}", paren_wrapped_vec(items.iter().map(|x| x.to_repl(symbol_table)))),
}
}
fn is_true(&self) -> bool {
match self {
Node::Expr(Expr::Lit(crate::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, symbol_table: &SymbolTable) -> String {
use self::Lit::*;
use self::Func::*;
let _ = symbol_table;
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(builtin) => format!("<built-in function '{:?}'>", builtin),
UserDefined { name: None, .. } => format!("<function>"),
UserDefined { name: Some(name), .. } => format!("<function '{}'>", name),
},
Expr::Constructor { type_name, arity, .. } => {
format!("<constructor for `{}` arity {}>", type_name, arity)
},
Expr::Tuple(exprs) => paren_wrapped_vec(exprs.iter().map(|x| x.to_repl(symbol_table))),
_ => format!("{:?}", self),
}
}
fn replace_conditional_target_sigil(self, replacement: &Expr) -> Expr {
use self::Expr::*;
match self {
ConditionalTargetSigilValue => replacement.clone(),
Unit | Lit(_) | Func(_) | Sym(_) | Constructor { .. } |
CaseMatch { .. } | UnimplementedSigilValue | ReductionError(_) => 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 => {
let ref symbol_table = self.symbol_table_handle.borrow();
acc.push(Ok(output.to_repl(symbol_table)))
},
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),
Sym(v) => self.handle_sym(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")),
ReductionError(err) => Err(format!("Reduction error: {}", err)),
}
}
}
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 {} arg(s)", 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(builtin) => Ok(self.apply_builtin(builtin, 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, builtin: Builtin, args: Vec<Expr>) -> EvalResult<Node> {
use self::Expr::*;
use self::Lit::*;
use Builtin::*;
let evaled_args: Result<Vec<Node>, String> = args.into_iter().map(|arg| self.expression(arg.to_node()))
.collect();
let evaled_args = evaled_args?;
Ok(match (builtin, evaled_args.as_slice()) {
(FieldAccess, &[Node::PrimObject { .. }]) => {
//TODO implement field access
unimplemented!()
},
(binop, &[Node::Expr(ref lhs), Node::Expr(ref rhs)]) => match (binop, lhs, rhs) {
/* binops */
(Add, Lit(Nat(l)), Lit(Nat(r))) => Lit(Nat(l + r)),
(Concatenate, Lit(StringLit(ref s1)), Lit(StringLit(ref s2))) => Lit(StringLit(Rc::new(format!("{}{}", s1, s2)))),
(Subtract, Lit(Nat(l)), Lit(Nat(r))) => Lit(Nat(l - r)),
(Multiply, Lit(Nat(l)), Lit(Nat(r))) => Lit(Nat(l * r)),
(Divide, Lit(Nat(l)), Lit(Nat(r))) => Lit(Float((*l as f64)/ (*r as f64))),
(Quotient, Lit(Nat(l)), Lit(Nat(r))) => if *r == 0 {
return Err(format!("divide by zero"));
} else {
Lit(Nat(l / r))
},
(Modulo, Lit(Nat(l)), Lit(Nat(r))) => Lit(Nat(l % r)),
(Exponentiation, Lit(Nat(l)), Lit(Nat(r))) => Lit(Nat(l ^ r)),
(BitwiseAnd, Lit(Nat(l)), Lit(Nat(r))) => Lit(Nat(l & r)),
(BitwiseOr, Lit(Nat(l)), Lit(Nat(r))) => Lit(Nat(l | r)),
/* comparisons */
(Equality, Lit(Nat(l)), Lit(Nat(r))) => Lit(Bool(l == r)),
(Equality, Lit(Int(l)), Lit(Int(r))) => Lit(Bool(l == r)),
(Equality, Lit(Float(l)), Lit(Float(r))) => Lit(Bool(l == r)),
(Equality, Lit(Bool(l)), Lit(Bool(r))) => Lit(Bool(l == r)),
(Equality, Lit(StringLit(ref l)), Lit(StringLit(ref r))) => Lit(Bool(l == r)),
(LessThan, Lit(Nat(l)), Lit(Nat(r))) => Lit(Bool(l < r)),
(LessThan, Lit(Int(l)), Lit(Int(r))) => Lit(Bool(l < r)),
(LessThan, Lit(Float(l)), Lit(Float(r))) => Lit(Bool(l < r)),
(LessThanOrEqual, Lit(Nat(l)), Lit(Nat(r))) => Lit(Bool(l <= r)),
(LessThanOrEqual, Lit(Int(l)), Lit(Int(r))) => Lit(Bool(l <= r)),
(LessThanOrEqual, Lit(Float(l)), Lit(Float(r))) => Lit(Bool(l <= r)),
(GreaterThan, Lit(Nat(l)), Lit(Nat(r))) => Lit(Bool(l > r)),
(GreaterThan, Lit(Int(l)), Lit(Int(r))) => Lit(Bool(l > r)),
(GreaterThan, Lit(Float(l)), Lit(Float(r))) => Lit(Bool(l > r)),
(GreaterThanOrEqual, Lit(Nat(l)), Lit(Nat(r))) => Lit(Bool(l >= r)),
(GreaterThanOrEqual, Lit(Int(l)), Lit(Int(r))) => Lit(Bool(l >= r)),
(GreaterThanOrEqual, Lit(Float(l)), Lit(Float(r))) => Lit(Bool(l >= r)),
_ => return Err("No valid binop".to_string())
}.to_node(),
(prefix, &[Node::Expr(ref arg)]) => match (prefix, arg) {
(BooleanNot, Lit(Bool(true))) => Lit(Bool(false)),
(BooleanNot, Lit(Bool(false))) => Lit(Bool(true)),
(Negate, Lit(Nat(n))) => Lit(Int(-1*(*n as i64))),
(Negate, Lit(Int(n))) => Lit(Int(-1*(*n as i64))),
(Increment, Lit(Int(n))) => Lit(Int(*n)),
(Increment, Lit(Nat(n))) => Lit(Nat(*n)),
_ => return Err("No valid prefix op".to_string())
}.to_node(),
/* builtin functions */
(IOPrint, &[ref anything]) => {
let ref symbol_table = self.symbol_table_handle.borrow();
print!("{}", anything.to_repl(symbol_table));
Expr::Unit.to_node()
},
(IOPrintLn, &[ref anything]) => {
let ref symbol_table = self.symbol_table_handle.borrow();
println!("{}", anything.to_repl(symbol_table));
Expr::Unit.to_node()
},
(IOGetLine, &[]) => {
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()))).to_node()
},
(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::Sym(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.matchable.guard, &cond)? {
continue;
}
match cond {
Node::PrimObject { ref tag, ref items, .. } => {
if alt.matchable.tag.map(|t| t == *tag).unwrap_or(true) {
let mut inner_state = self.new_frame(items, &alt.matchable.bound_vars);
if all_subpatterns_pass(&mut inner_state, &alt.matchable.subpatterns, items)? {
return inner_state.block(alt.item);
} else {
continue;
}
}
},
Node::PrimTuple { ref items } => {
let mut inner_state = self.new_frame(items, &alt.matchable.bound_vars);
if all_subpatterns_pass(&mut inner_state, &alt.matchable.subpatterns, items)? {
return inner_state.block(alt.item);
} else {
continue;
}
},
Node::Expr(ref _e) => {
if let None = alt.matchable.tag {
return self.block(alt.item)
}
}
}
}
Err(format!("{:?} failed pattern match", cond))
}
//TODO if I don't need to lookup by name here...
fn handle_sym(&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_fqsn(&fqsn!(name ; tr));
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!(),
},
SymbolSpec::RecordConstructor { .. } => return Err(format!("This shouldn't be a record!")),
SymbolSpec::Binding => match self.values.lookup(&name) {
Some(Binding { val, .. }) => val.clone(),
None => return Err(format!("Symbol {} exists in symbol table but not in evaluator table", name))
}
},
//TODO ideally this should be returning a runtime error if this is ever None, but it's not
//handling all bindings correctly yet
//None => return Err(format!("Couldn't find value {}", name)),
None => match self.values.lookup(&name) {
Some(Binding { val, .. }) => val.clone(),
None => return Err(format!("Couldn't find value {}", name)),
}
})
}
}