schala/schala-lang/language/src/tree_walk_eval/mod.rs

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use crate::reduced_ir::{ReducedIR, Expression, Lookup, Function, FunctionDefinition, Statement, Literal};
use crate::symbol_table::{DefId};
use crate::util::ScopeStack;
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use crate::builtin::Builtin;
use std::fmt::Write;
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use std::rc::Rc;
use std::convert::From;
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mod test;
type EvalResult<T> = Result<T, String>;
#[derive(Debug)]
pub struct State<'a> {
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environments: ScopeStack<'a, Memory, RuntimeValue>,
}
//TODO - eh, I dunno, maybe it doesn't matter exactly how memory works in the tree-walking
//evaluator
#[derive(Debug, PartialEq, Eq, Hash, Clone)]
enum Memory {
Index(u32)
}
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// This is for function param lookups, and is a hack
impl From<u8> for Memory {
fn from(n: u8) -> Self {
Memory::Index(4_000_000 + (n as u32))
}
}
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impl From<&DefId> for Memory {
fn from(id: &DefId) -> Self {
Self::Index(id.as_u32())
}
}
#[derive(Debug)]
struct RuntimeError {
msg: String
}
impl From<String> for RuntimeError {
fn from(msg: String) -> Self {
Self {
msg
}
}
}
impl RuntimeError {
fn get_msg(&self) -> String {
format!("Runtime error: {}", self.msg)
}
}
fn paren_wrapped(terms: impl Iterator<Item=String>) -> String {
let mut buf = String::new();
write!(buf, "(").unwrap();
for term in terms.map(Some).intersperse(None) {
match term {
Some(e) => write!(buf, "{}", e).unwrap(),
None => write!(buf, ", ").unwrap(),
};
}
write!(buf, ")").unwrap();
buf
}
#[derive(Debug)]
enum RuntimeValue {
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Function(FunctionDefinition),
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Primitive(Primitive),
}
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impl From<Primitive> for RuntimeValue {
fn from(prim: Primitive) -> Self {
Self::Primitive(prim)
}
}
fn expr_to_repl(expr: &Expression) -> String {
match expr {
Expression::Literal(lit) => match lit {
Literal::Nat(n) => format!("{}", n),
Literal::Int(i) => format!("{}", i),
Literal::Float(f) => format!("{}", f),
Literal::Bool(b) => format!("{}", b),
Literal::StringLit(s) => format!("\"{}\"", s),
}
Expression::Tuple(terms) => paren_wrapped(terms.iter().map(|x| expr_to_repl(x))),
Expression::Assign { lval, rval } => {
"".to_string()
},
e => format!("Expression {:?} shouldn't be here", e),
}
}
impl RuntimeValue {
fn to_repl(&self) -> String {
match self {
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RuntimeValue::Primitive(ref prim) => expr_to_repl(&prim.to_expr()),
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RuntimeValue::Function(ref expr) => "<function>".to_string(),
}
}
}
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/// A fully-reduced value
#[derive(Debug, Clone)]
enum Primitive {
Tuple(Vec<Primitive>),
Literal(Literal),
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Callable(Function),
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/*
PrimObject {
name: Rc<String>,
tag: usize,
items: Vec<Node>,
},
*/
}
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impl From<Literal> for Primitive {
fn from(lit: Literal) -> Self {
Primitive::Literal(lit)
}
}
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impl Primitive {
fn to_expr(&self) -> Expression {
match self {
Primitive::Tuple(items) => Expression::Tuple(items.iter().map(|item| item.to_expr()).collect()),
Primitive::Literal(lit) => Expression::Literal(lit.clone()),
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Primitive::Callable(function) => Expression::Callable(function.clone()),
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}
}
}
impl<'a> State<'a> {
pub fn new() -> Self {
Self {
environments: ScopeStack::new(Some("global".to_string()))
}
}
pub fn evaluate(&mut self, reduced: ReducedIR, repl: bool) -> Vec<Result<String, String>> {
let mut acc = vec![];
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for (def_id, function) in reduced.functions.into_iter() {
let mem = (&def_id).into();
self.environments.insert(mem, RuntimeValue::Function(function));
}
for statement in reduced.entrypoint.into_iter() {
match self.statement(statement) {
Ok(Some(output)) if repl => {
acc.push(Ok(output.to_repl()))
},
Ok(_) => (),
Err(error) => {
acc.push(Err(error.into()));
return acc;
}
}
}
acc
}
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fn block(&mut self, statements: Vec<Statement>) -> EvalResult<Primitive> {
//TODO need to handle breaks, returns, etc.
let mut ret = None;
for stmt in statements.into_iter() {
if let Some(RuntimeValue::Primitive(prim)) = self.statement(stmt)? {
ret = Some(prim);
}
}
Ok(if let Some(ret) = ret {
ret
} else {
self.expression(Expression::unit())?
})
}
fn statement(&mut self, stmt: Statement) -> EvalResult<Option<RuntimeValue>> {
match stmt {
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Statement::Binding { ref id, expr, constant } => {
println!("eval() binding id: {}", id);
let evaluated = self.expression(expr)?;
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self.environments.insert(id.into(), evaluated.into());
Ok(None)
},
Statement::Expression(expr) => {
let evaluated = self.expression(expr)?;
Ok(Some(evaluated.into()))
}
}
}
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fn expression(&mut self, expression: Expression) -> EvalResult<Primitive> {
Ok(match expression {
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Expression::Literal(lit) => Primitive::Literal(lit),
Expression::Tuple(items) => Primitive::Tuple(items.into_iter().map(|expr| self.expression(expr)).collect::<EvalResult<Vec<Primitive>>>()?),
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Expression::Lookup { ref id, kind } => {
match kind {
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Lookup::Function => {
let mem = id.into();
match self.environments.lookup(&mem) {
// This just checks that the function exists in "memory" by ID, we don't
// actually retrieve it until `apply_function()`
Some(RuntimeValue::Function(_)) => Primitive::Callable(Function::UserDefined(id.clone())),
x => return Err(format!("Function not found for id: {} : {:?}", id, x)),
}
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},
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Lookup::Param(n) => {
let mem = n.into();
match self.environments.lookup(&mem) {
Some(RuntimeValue::Primitive(prim)) => prim.clone(),
e => return Err(format!("Param lookup error, got {:?}", e)),
}
},
kind @ Lookup::LocalVar | kind @ Lookup::GlobalVar => {
let mem = id.into();
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match self.environments.lookup(&mem) {
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Some(RuntimeValue::Primitive(expr)) => expr.clone(),
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_ => return Err(format!("Nothing found for variable lookup {} of kind {:?}", id, kind)),
}
},
}
},
Expression::Assign { ref lval, box rval } => {
let mem = lval.into();
let mut env = self.environments.lookup(&mem);
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return Err("Assign not implemented".to_string());
},
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Expression::Call { box f, args } => self.call_expression(f, args)?,
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Expression::Callable(func) => Primitive::Callable(func),
Expression::ReductionError(e) => return Err(e.into()),
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e => return Err(format!("Can't yet handle {:?}", e)),
})
}
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fn call_expression(&mut self, f: Expression, args: Vec<Expression>) -> EvalResult<Primitive> {
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let func = match self.expression(f)? {
Primitive::Callable(func) => func,
other => return Err(format!("Trying to call non-function value: {:?}", other)),
};
match func {
Function::Builtin(builtin) => self.apply_builtin(builtin, args),
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Function::UserDefined(def_id) => {
let mem = (&def_id).into();
match self.environments.lookup(&mem) {
Some(RuntimeValue::Function(FunctionDefinition { body })) => {
let body = body.clone(); //TODO ideally this clone would not happen
self.apply_function(body, args)
},
e => Err(format!("Error looking up function with id {}: {:?}", def_id, e))
}
},
Function::Lambda { arity, body } => {
if arity as usize != args.len() {
return Err(format!("Lambda expression requries {} arguments, only {} provided", arity, args.len()));
}
let body = body.clone(); //TODO again ideally, no cloning here
self.apply_function(body, args)
}
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}
}
fn apply_builtin(&mut self, builtin: Builtin, args: Vec<Expression>) -> EvalResult<Primitive> {
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use Builtin::*;
use Literal::*;
use Expression::Literal as Lit;
let evaled_args: EvalResult<Vec<Expression>> =
args.into_iter().map(|arg| self.expression(arg).map(|prim| prim.to_expr())).collect();
let evaled_args = evaled_args?;
Ok(match (builtin, evaled_args.as_slice()) {
(FieldAccess, /*&[Node::PrimObject { .. }]*/ _) => {
return Err("Field access unimplemented".to_string());
}
(binop, &[ref lhs, ref rhs]) => match (binop, lhs, rhs) {
(Add, Lit(Nat(l)), Lit(Nat(r))) => Nat(l + r).into(),
(Concatenate, Lit(StringLit(ref s1)), Lit(StringLit(ref s2))) => StringLit(Rc::new(format!("{}{}", s1, s2))).into(),
(Subtract, Lit(Nat(l)), Lit(Nat(r))) => Nat(l - r).into(),
(Multiply, Lit(Nat(l)), Lit(Nat(r))) => Nat(l * r).into(),
(Divide, Lit(Nat(l)), Lit(Nat(r))) => Float((*l as f64)/ (*r as f64)).into(),
(Quotient, Lit(Nat(l)), Lit(Nat(r))) => if *r == 0 {
return Err("Divide-by-zero error".to_string());
} else {
Nat(l / r).into()
},
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(Modulo, Lit(Nat(l)), Lit(Nat(r))) => Nat(l % r).into(),
(Exponentiation, Lit(Nat(l)), Lit(Nat(r))) => Nat(l ^ r).into(),
(BitwiseAnd, Lit(Nat(l)), Lit(Nat(r))) => Nat(l & r).into(),
(BitwiseOr, Lit(Nat(l)), Lit(Nat(r))) => Nat(l | r).into(),
/* comparisons */
(Equality, Lit(Nat(l)), Lit(Nat(r))) => Bool(l == r).into(),
(Equality, Lit(Int(l)), Lit(Int(r))) => Bool(l == r).into(),
(Equality, Lit(Float(l)), Lit(Float(r))) => Bool(l == r).into(),
(Equality, Lit(Bool(l)), Lit(Bool(r))) => Bool(l == r).into(),
(Equality, Lit(StringLit(ref l)), Lit(StringLit(ref r))) => Bool(l == r).into(),
(LessThan, Lit(Nat(l)), Lit(Nat(r))) => Bool(l < r).into(),
(LessThan, Lit(Int(l)), Lit(Int(r))) => Bool(l < r).into(),
(LessThan, Lit(Float(l)), Lit(Float(r))) => Bool(l < r).into(),
(LessThanOrEqual, Lit(Nat(l)), Lit(Nat(r))) => Bool(l <= r).into(),
(LessThanOrEqual, Lit(Int(l)), Lit(Int(r))) => Bool(l <= r).into(),
(LessThanOrEqual, Lit(Float(l)), Lit(Float(r))) => Bool(l <= r).into(),
(GreaterThan, Lit(Nat(l)), Lit(Nat(r))) => Bool(l > r).into(),
(GreaterThan, Lit(Int(l)), Lit(Int(r))) => Bool(l > r).into(),
(GreaterThan, Lit(Float(l)), Lit(Float(r))) => Bool(l > r).into(),
(GreaterThanOrEqual, Lit(Nat(l)), Lit(Nat(r))) => Bool(l >= r).into(),
(GreaterThanOrEqual, Lit(Int(l)), Lit(Int(r))) => Bool(l >= r).into(),
(GreaterThanOrEqual, Lit(Float(l)), Lit(Float(r))) => Bool(l >= r).into(),
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(binop, lhs, rhs) => return Err(format!("Invalid binop expression {:?} {:?} {:?}", lhs, binop, rhs)),
},
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(prefix, &[ref arg]) => match (prefix, arg) {
(BooleanNot, Lit(Bool(true))) => Bool(false),
(BooleanNot, Lit(Bool(false))) => Bool(true),
(Negate, Lit(Nat(n))) => Int(-(*n as i64)),
(Negate, Lit(Int(n))) => Int(-(*n as i64)),
(Increment, Lit(Int(n))) => Int(*n),
(Increment, Lit(Nat(n))) => Nat(*n),
_ => return Err("No valid prefix op".to_string())
}.into(),
/* builtin functions */
(IOPrint, &[ref anything]) => {
print!("{}", expr_to_repl(anything));
Primitive::Tuple(vec![])
},
(IOPrintLn, &[ref anything]) => {
println!("{}", expr_to_repl(anything));
Primitive::Tuple(vec![])
},
(IOGetLine, &[]) => {
let mut buf = String::new();
std::io::stdin().read_line(&mut buf).expect("Error readling line in 'getline'");
StringLit(Rc::new(buf.trim().to_string())).into()
},
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(x, args) => return Err(format!("bad or unimplemented builtin {:?} | {:?}", x, args)),
})
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}
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fn apply_function(&mut self, body: Vec<Statement>, args: Vec<Expression>) -> EvalResult<Primitive> {
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let mut evaluated_args: Vec<Primitive> = vec![];
for arg in args.into_iter() {
evaluated_args.push(self.expression(arg)?);
}
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let mut frame_state = State {
environments: self.environments.new_scope(None)
};
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for (n, evaled) in evaluated_args.into_iter().enumerate() {
let n = n as u8;
let mem = n.into();
frame_state.environments.insert(mem, RuntimeValue::Primitive(evaled));
}
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frame_state.block(body)
}
}