503 lines
18 KiB
Rust
503 lines
18 KiB
Rust
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use std::cell::RefCell;
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use std::rc::Rc;
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use std::fmt::Write;
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use std::io;
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use itertools::Itertools;
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use crate::util::ScopeStack;
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use crate::reduced_ast::{BoundVars, ReducedAST, Stmt, Expr, Lit, Func, Alternative, Subpattern};
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use crate::symbol_table::{SymbolSpec, Symbol, SymbolTable, ScopeSegment, ScopeSegmentKind, FullyQualifiedSymbolName};
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use crate::builtin::Builtin;
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mod test;
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pub struct State<'a> {
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values: ScopeStack<'a, Rc<String>, ValueEntry>,
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symbol_table_handle: Rc<RefCell<SymbolTable>>,
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}
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impl<'a> State<'a> {
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pub fn new(symbol_table_handle: Rc<RefCell<SymbolTable>>) -> State<'a> {
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let values = ScopeStack::new(Some(format!("global")));
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State { values, symbol_table_handle }
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}
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pub fn debug_print(&self) -> String {
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format!("Values: {:?}", self.values)
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}
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fn new_frame(&'a self, items: &'a Vec<Node>, bound_vars: &BoundVars) -> State<'a> {
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let mut inner_state = State {
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values: self.values.new_scope(None),
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symbol_table_handle: self.symbol_table_handle.clone(),
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};
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for (bound_var, val) in bound_vars.iter().zip(items.iter()) {
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if let Some(bv) = bound_var.as_ref() {
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inner_state.values.insert(bv.clone(), ValueEntry::Binding { constant: true, val: val.clone() });
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}
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}
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inner_state
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}
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}
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#[derive(Debug, Clone)]
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enum Node {
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Expr(Expr),
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PrimObject {
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name: Rc<String>,
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tag: usize,
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items: Vec<Node>,
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},
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PrimTuple {
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items: Vec<Node>
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}
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}
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fn paren_wrapped_vec(terms: impl Iterator<Item=String>) -> String {
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let mut buf = String::new();
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write!(buf, "(").unwrap();
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for term in terms.map(|e| Some(e)).intersperse(None) {
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match term {
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Some(e) => write!(buf, "{}", e).unwrap(),
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None => write!(buf, ", ").unwrap(),
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};
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}
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write!(buf, ")").unwrap();
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buf
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}
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impl Node {
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fn to_repl(&self, symbol_table: &SymbolTable) -> String {
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match self {
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Node::Expr(e) => e.to_repl(symbol_table),
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Node::PrimObject { name, items, .. } if items.len() == 0 => format!("{}", name),
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Node::PrimObject { name, items, .. } => format!("{}{}", name, paren_wrapped_vec(items.iter().map(|x| x.to_repl(symbol_table)))),
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Node::PrimTuple { items } => format!("{}", paren_wrapped_vec(items.iter().map(|x| x.to_repl(symbol_table)))),
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}
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}
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fn is_true(&self) -> bool {
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match self {
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Node::Expr(Expr::Lit(crate::reduced_ast::Lit::Bool(true))) => true,
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_ => false,
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}
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}
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}
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#[derive(Debug)]
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enum ValueEntry {
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Binding {
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constant: bool,
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val: /*FullyEvaluatedExpr*/ Node, //TODO make this use a subtype to represent fully evaluatedness
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}
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}
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type EvalResult<T> = Result<T, String>;
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impl Expr {
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fn to_node(self) -> Node {
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Node::Expr(self)
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}
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fn to_repl(&self, symbol_table: &SymbolTable) -> String {
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use self::Lit::*;
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use self::Func::*;
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let _ = symbol_table;
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match self {
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Expr::Lit(ref l) => match l {
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Nat(n) => format!("{}", n),
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Int(i) => format!("{}", i),
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Float(f) => format!("{}", f),
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Bool(b) => format!("{}", b),
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StringLit(s) => format!("\"{}\"", s),
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},
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Expr::Func(f) => match f {
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BuiltIn(builtin) => format!("<built-in function '{:?}'>", builtin),
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UserDefined { name: None, .. } => format!("<function>"),
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UserDefined { name: Some(name), .. } => format!("<function '{}'>", name),
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},
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Expr::Constructor { type_name, arity, .. } => {
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format!("<constructor for `{}` arity {}>", type_name, arity)
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},
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Expr::Tuple(exprs) => paren_wrapped_vec(exprs.iter().map(|x| x.to_repl(symbol_table))),
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_ => format!("{:?}", self),
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}
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}
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fn replace_conditional_target_sigil(self, replacement: &Expr) -> Expr {
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use self::Expr::*;
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match self {
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ConditionalTargetSigilValue => replacement.clone(),
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Unit | Lit(_) | Func(_) | Sym(_) | Constructor { .. } |
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CaseMatch { .. } | UnimplementedSigilValue | ReductionError(_) => self,
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Tuple(exprs) => Tuple(exprs.into_iter().map(|e| e.replace_conditional_target_sigil(replacement)).collect()),
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Call { f, args } => {
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let new_args = args.into_iter().map(|e| e.replace_conditional_target_sigil(replacement)).collect();
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Call { f, args: new_args }
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},
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Conditional { .. } => panic!("Dunno if I need this, but if so implement"),
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Assign { .. } => panic!("I'm pretty sure I don't need this"),
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}
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}
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}
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impl<'a> State<'a> {
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pub fn evaluate(&mut self, ast: ReducedAST, repl: bool) -> Vec<Result<String, String>> {
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let mut acc = vec![];
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// handle prebindings
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for statement in ast.0.iter() {
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self.prebinding(statement);
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}
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for statement in ast.0 {
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match self.statement(statement) {
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Ok(Some(ref output)) if repl => {
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let ref symbol_table = self.symbol_table_handle.borrow();
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acc.push(Ok(output.to_repl(symbol_table)))
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},
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Ok(_) => (),
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Err(error) => {
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acc.push(Err(format!("Runtime error: {}", error)));
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return acc;
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},
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}
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}
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acc
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}
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fn prebinding(&mut self, stmt: &Stmt) {
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match stmt {
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Stmt::PreBinding { name, func } => {
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let v_entry = ValueEntry::Binding { constant: true, val: Node::Expr(Expr::Func(func.clone())) };
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self.values.insert(name.clone(), v_entry);
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},
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Stmt::Expr(_expr) => {
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//TODO have this support things like nested function defs
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},
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_ => ()
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}
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}
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fn statement(&mut self, stmt: Stmt) -> EvalResult<Option<Node>> {
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match stmt {
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Stmt::Binding { name, constant, expr } => {
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let val = self.expression(Node::Expr(expr))?;
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self.values.insert(name.clone(), ValueEntry::Binding { constant, val });
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Ok(None)
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},
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Stmt::Expr(expr) => Ok(Some(self.expression(expr.to_node())?)),
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Stmt::PreBinding {..} | Stmt::Noop => Ok(None),
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}
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}
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fn block(&mut self, stmts: Vec<Stmt>) -> EvalResult<Node> {
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let mut ret = None;
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for stmt in stmts {
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ret = self.statement(stmt)?;
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}
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Ok(ret.unwrap_or(Node::Expr(Expr::Unit)))
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}
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fn expression(&mut self, node: Node) -> EvalResult<Node> {
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use self::Expr::*;
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match node {
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t @ Node::PrimTuple { .. } => Ok(t),
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obj @ Node::PrimObject { .. } => Ok(obj),
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Node::Expr(expr) => match expr {
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literal @ Lit(_) => Ok(Node::Expr(literal)),
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Call { box f, args } => self.call_expression(f, args),
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Sym(v) => self.handle_sym(v),
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Constructor { arity, ref name, tag, .. } if arity == 0 => Ok(Node::PrimObject { name: name.clone(), tag, items: vec![] }),
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constructor @ Constructor { .. } => Ok(Node::Expr(constructor)),
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func @ Func(_) => Ok(Node::Expr(func)),
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Tuple(exprs) => {
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let nodes = exprs.into_iter().map(|expr| self.expression(Node::Expr(expr))).collect::<Result<Vec<Node>,_>>()?;
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Ok(Node::PrimTuple { items: nodes })
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},
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Conditional { box cond, then_clause, else_clause } => self.conditional(cond, then_clause, else_clause),
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Assign { box val, box expr } => self.assign_expression(val, expr),
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Unit => Ok(Node::Expr(Unit)),
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CaseMatch { box cond, alternatives } => self.case_match_expression(cond, alternatives),
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ConditionalTargetSigilValue => Ok(Node::Expr(ConditionalTargetSigilValue)),
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UnimplementedSigilValue => Err(format!("Sigil value eval not implemented")),
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ReductionError(err) => Err(format!("Reduction error: {}", err)),
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}
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}
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}
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fn call_expression(&mut self, f: Expr, args: Vec<Expr>) -> EvalResult<Node> {
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use self::Expr::*;
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match self.expression(Node::Expr(f))? {
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Node::Expr(Constructor { type_name, name, tag, arity }) => self.apply_data_constructor(type_name, name, tag, arity, args),
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Node::Expr(Func(f)) => self.apply_function(f, args),
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other => return Err(format!("Tried to call {:?} which is not a function or data constructor", other)),
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}
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}
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fn apply_data_constructor(&mut self, _type_name: Rc<String>, name: Rc<String>, tag: usize, arity: usize, args: Vec<Expr>) -> EvalResult<Node> {
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if arity != args.len() {
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return Err(format!("Data constructor {} requires {} arg(s)", name, arity));
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}
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let evaled_args = args.into_iter().map(|expr| self.expression(Node::Expr(expr))).collect::<Result<Vec<Node>,_>>()?;
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//let evaled_args = vec![];
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Ok(Node::PrimObject {
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name: name.clone(),
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items: evaled_args,
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tag
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})
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}
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fn apply_function(&mut self, f: Func, args: Vec<Expr>) -> EvalResult<Node> {
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match f {
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Func::BuiltIn(builtin) => Ok(self.apply_builtin(builtin, args)?),
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Func::UserDefined { params, body, name } => {
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if params.len() != args.len() {
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return Err(format!("calling a {}-argument function with {} args", params.len(), args.len()))
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}
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let mut func_state = State {
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values: self.values.new_scope(name.map(|n| format!("{}", n))),
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symbol_table_handle: self.symbol_table_handle.clone(),
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};
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for (param, val) in params.into_iter().zip(args.into_iter()) {
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let val = func_state.expression(Node::Expr(val))?;
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func_state.values.insert(param, ValueEntry::Binding { constant: true, val });
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}
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// TODO figure out function return semantics
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func_state.block(body)
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}
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}
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}
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fn apply_builtin(&mut self, builtin: Builtin, args: Vec<Expr>) -> EvalResult<Node> {
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use self::Expr::*;
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use self::Lit::*;
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use Builtin::*;
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let evaled_args: Result<Vec<Node>, String> = args.into_iter().map(|arg| self.expression(arg.to_node()))
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.collect();
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let evaled_args = evaled_args?;
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Ok(match (builtin, evaled_args.as_slice()) {
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(FieldAccess, &[Node::PrimObject { .. }]) => {
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//TODO implement field access
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unimplemented!()
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},
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(binop, &[Node::Expr(ref lhs), Node::Expr(ref rhs)]) => match (binop, lhs, rhs) {
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/* binops */
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(Add, Lit(Nat(l)), Lit(Nat(r))) => Lit(Nat(l + r)),
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(Concatenate, Lit(StringLit(ref s1)), Lit(StringLit(ref s2))) => Lit(StringLit(Rc::new(format!("{}{}", s1, s2)))),
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(Subtract, Lit(Nat(l)), Lit(Nat(r))) => Lit(Nat(l - r)),
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(Multiply, Lit(Nat(l)), Lit(Nat(r))) => Lit(Nat(l * r)),
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(Divide, Lit(Nat(l)), Lit(Nat(r))) => Lit(Float((*l as f64)/ (*r as f64))),
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(Quotient, Lit(Nat(l)), Lit(Nat(r))) => if *r == 0 {
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return Err(format!("divide by zero"));
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} else {
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Lit(Nat(l / r))
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},
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(Modulo, Lit(Nat(l)), Lit(Nat(r))) => Lit(Nat(l % r)),
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(Exponentiation, Lit(Nat(l)), Lit(Nat(r))) => Lit(Nat(l ^ r)),
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(BitwiseAnd, Lit(Nat(l)), Lit(Nat(r))) => Lit(Nat(l & r)),
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(BitwiseOr, Lit(Nat(l)), Lit(Nat(r))) => Lit(Nat(l | r)),
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/* comparisons */
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(Equality, Lit(Nat(l)), Lit(Nat(r))) => Lit(Bool(l == r)),
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(Equality, Lit(Int(l)), Lit(Int(r))) => Lit(Bool(l == r)),
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(Equality, Lit(Float(l)), Lit(Float(r))) => Lit(Bool(l == r)),
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(Equality, Lit(Bool(l)), Lit(Bool(r))) => Lit(Bool(l == r)),
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(Equality, Lit(StringLit(ref l)), Lit(StringLit(ref r))) => Lit(Bool(l == r)),
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(LessThan, Lit(Nat(l)), Lit(Nat(r))) => Lit(Bool(l < r)),
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(LessThan, Lit(Int(l)), Lit(Int(r))) => Lit(Bool(l < r)),
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(LessThan, Lit(Float(l)), Lit(Float(r))) => Lit(Bool(l < r)),
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(LessThanOrEqual, Lit(Nat(l)), Lit(Nat(r))) => Lit(Bool(l <= r)),
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(LessThanOrEqual, Lit(Int(l)), Lit(Int(r))) => Lit(Bool(l <= r)),
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(LessThanOrEqual, Lit(Float(l)), Lit(Float(r))) => Lit(Bool(l <= r)),
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(GreaterThan, Lit(Nat(l)), Lit(Nat(r))) => Lit(Bool(l > r)),
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(GreaterThan, Lit(Int(l)), Lit(Int(r))) => Lit(Bool(l > r)),
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(GreaterThan, Lit(Float(l)), Lit(Float(r))) => Lit(Bool(l > r)),
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(GreaterThanOrEqual, Lit(Nat(l)), Lit(Nat(r))) => Lit(Bool(l >= r)),
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(GreaterThanOrEqual, Lit(Int(l)), Lit(Int(r))) => Lit(Bool(l >= r)),
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(GreaterThanOrEqual, Lit(Float(l)), Lit(Float(r))) => Lit(Bool(l >= r)),
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_ => return Err("No valid binop".to_string())
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}.to_node(),
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(prefix, &[Node::Expr(ref arg)]) => match (prefix, arg) {
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(BooleanNot, Lit(Bool(true))) => Lit(Bool(false)),
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(BooleanNot, Lit(Bool(false))) => Lit(Bool(true)),
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(Negate, Lit(Nat(n))) => Lit(Int(-1*(*n as i64))),
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(Negate, Lit(Int(n))) => Lit(Int(-1*(*n as i64))),
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(Increment, Lit(Int(n))) => Lit(Int(*n)),
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(Increment, Lit(Nat(n))) => Lit(Nat(*n)),
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_ => return Err("No valid prefix op".to_string())
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}.to_node(),
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/* builtin functions */
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(IOPrint, &[ref anything]) => {
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let ref symbol_table = self.symbol_table_handle.borrow();
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print!("{}", anything.to_repl(symbol_table));
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Expr::Unit.to_node()
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},
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(IOPrintLn, &[ref anything]) => {
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let ref symbol_table = self.symbol_table_handle.borrow();
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println!("{}", anything.to_repl(symbol_table));
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Expr::Unit.to_node()
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},
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(IOGetLine, &[]) => {
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let mut buf = String::new();
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io::stdin().read_line(&mut buf).expect("Error readling line in 'getline'");
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Lit(StringLit(Rc::new(buf.trim().to_string()))).to_node()
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},
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(x, args) => return Err(format!("bad or unimplemented builtin {:?} | {:?}", x, args)),
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})
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}
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fn conditional(&mut self, cond: Expr, then_clause: Vec<Stmt>, else_clause: Vec<Stmt>) -> EvalResult<Node> {
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let cond = self.expression(Node::Expr(cond))?;
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Ok(match cond {
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Node::Expr(Expr::Lit(Lit::Bool(true))) => self.block(then_clause)?,
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Node::Expr(Expr::Lit(Lit::Bool(false))) => self.block(else_clause)?,
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_ => return Err(format!("Conditional with non-boolean condition"))
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})
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}
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fn assign_expression(&mut self, val: Expr, expr: Expr) -> EvalResult<Node> {
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let name = match val {
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Expr::Sym(name) => name,
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_ => return Err(format!("Trying to assign to a non-value")),
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};
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let constant = match self.values.lookup(&name) {
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None => return Err(format!("Constant {} is undefined", name)),
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Some(ValueEntry::Binding { constant, .. }) => constant.clone(),
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};
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if constant {
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return Err(format!("trying to update {}, a non-mutable binding", name));
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}
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let val = self.expression(Node::Expr(expr))?;
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self.values.insert(name.clone(), ValueEntry::Binding { constant: false, val });
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Ok(Node::Expr(Expr::Unit))
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}
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fn guard_passes(&mut self, guard: &Option<Expr>, cond: &Node) -> EvalResult<bool> {
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if let Some(ref guard_expr) = guard {
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let guard_expr = match cond {
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Node::Expr(ref e) => guard_expr.clone().replace_conditional_target_sigil(e),
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_ => guard_expr.clone()
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};
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Ok(self.expression(guard_expr.to_node())?.is_true())
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} else {
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Ok(true)
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}
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}
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fn case_match_expression(&mut self, cond: Expr, alternatives: Vec<Alternative>) -> EvalResult<Node> {
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//TODO need to handle recursive subpatterns
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let all_subpatterns_pass = |state: &mut State, subpatterns: &Vec<Option<Subpattern>>, items: &Vec<Node>| -> EvalResult<bool> {
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if subpatterns.len() == 0 {
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return Ok(true)
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}
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if items.len() != subpatterns.len() {
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return Err(format!("Subpattern length isn't correct items {} subpatterns {}", items.len(), subpatterns.len()));
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}
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for (maybe_subp, cond) in subpatterns.iter().zip(items.iter()) {
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if let Some(subp) = maybe_subp {
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if !state.guard_passes(&subp.guard, &cond)? {
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return Ok(false)
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}
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}
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}
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Ok(true)
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};
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let cond = self.expression(Node::Expr(cond))?;
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for alt in alternatives {
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// no matter what type of condition we have, ignore alternative if the guard evaluates false
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if !self.guard_passes(&alt.matchable.guard, &cond)? {
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continue;
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}
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match cond {
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Node::PrimObject { ref tag, ref items, .. } => {
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if alt.matchable.tag.map(|t| t == *tag).unwrap_or(true) {
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let mut inner_state = self.new_frame(items, &alt.matchable.bound_vars);
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if all_subpatterns_pass(&mut inner_state, &alt.matchable.subpatterns, items)? {
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return inner_state.block(alt.item);
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|
} 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 { local_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: local_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)),
|
|
}
|
|
})
|
|
}
|
|
}
|