Improve name & documentation accuracy
Renamed ControlFlow -> HaltStatus because that's what the enum really is -- a status on why something halted. Also reviewed `interpret.rs`'s documentation and fixed a few things that were out of date.
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@ -24,8 +24,8 @@ pub struct ExecEnv {
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stack: Vec<Scope>,
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stack: Vec<Scope>,
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}
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}
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/// A set of visible variable and function definitions, which serves
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/// A set of visible variable and function definitions in a single
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/// as a context in which expressions can be evaluated.
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/// stack frame.
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#[derive(Default)]
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#[derive(Default)]
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struct Scope {
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struct Scope {
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/// The mapping from variable names to values.
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/// The mapping from variable names to values.
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@ -34,15 +34,17 @@ struct Scope {
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// other information.
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// other information.
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}
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}
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/// The result of successfully executing a set of statements.
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/// The reason a successful series of statements halted.
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enum ControlFlow {
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enum HaltStatus {
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/// The statements evaluated to this value.
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/// The last statement in the list evaluated to this value.
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Value(Value),
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Value(Value),
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/// A "break" statement occurred at the top level.
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/// A `break` statement occurred and was not caught by a `loop`
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/// statement.
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Break,
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Break,
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/// A "hopback" statement occurred at the top level.
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/// A `hopback` statement occurred and was not caught by a `loop`
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/// statement.
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Hopback,
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Hopback,
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}
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}
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@ -57,11 +59,12 @@ impl ExecEnv {
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/// Evaluate a set of Items in their own stack frame. Return the
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/// Evaluate a set of Items in their own stack frame. Return the
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/// value of the last Item evaluated, or an error if one or more
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/// value of the last Item evaluated, or an error if one or more
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/// of the Items failed to evaluate.
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/// of the Items failed to evaluate or if a `break` or `hopback`
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/// statement occurred at the top level.
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pub fn eval_items(&mut self, items: &[Item]) -> Result<Value, Error> {
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pub fn eval_items(&mut self, items: &[Item]) -> Result<Value, Error> {
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match self.eval_items_cf(items)? {
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match self.eval_items_hs(items)? {
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ControlFlow::Value(v) => Ok(v),
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HaltStatus::Value(v) => Ok(v),
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ControlFlow::Break | ControlFlow::Hopback => Err(Error {
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HaltStatus::Break | HaltStatus::Hopback => Err(Error {
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// It's an error to issue a `break` outside of a
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// It's an error to issue a `break` outside of a
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// `loop` statement.
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// `loop` statement.
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kind: ErrorKind::TopLevelBreak,
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kind: ErrorKind::TopLevelBreak,
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@ -70,16 +73,19 @@ impl ExecEnv {
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}
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}
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}
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}
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/// The same as `eval_items`, but reports "break" and "hopback"
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/// The same as `eval_items`, but report "break" and "hopback"
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/// exit codes as normal conditions in a ControlFlow enum.
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/// exit codes as normal conditions in a HaltStatus enum.
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fn eval_items_cf(&mut self, items: &[Item]) -> Result<ControlFlow, Error> {
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///
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/// `interpret`-internal code should typically prefer this
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/// function over `eval_items`.
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fn eval_items_hs(&mut self, items: &[Item]) -> Result<HaltStatus, Error> {
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let init_depth = self.stack.len();
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let init_depth = self.stack.len();
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self.stack.push(Default::default());
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self.stack.push(Default::default());
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let mut final_result = Ok(ControlFlow::Value(Value::Nul));
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let mut final_result = Ok(HaltStatus::Value(Value::Nul));
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for item in items {
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for item in items {
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final_result = self.eval_item(item);
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final_result = self.eval_item(item);
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if !matches!(final_result, Ok(ControlFlow::Value(_))) {
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if !matches!(final_result, Ok(HaltStatus::Value(_))) {
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break;
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break;
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}
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}
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}
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}
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@ -91,9 +97,9 @@ impl ExecEnv {
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}
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}
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/// Evaluate a single Item, returning its value or an error.
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/// Evaluate a single Item, returning its value or an error.
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fn eval_item(&mut self, item: &Item) -> Result<ControlFlow, Error> {
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fn eval_item(&mut self, item: &Item) -> Result<HaltStatus, Error> {
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match item {
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match item {
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Item::Expr(expr) => self.eval_expr(expr).map(|v| ControlFlow::Value(v)),
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Item::Expr(expr) => self.eval_expr(expr).map(|v| HaltStatus::Value(v)),
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Item::Stmt(stmt) => self.eval_stmt(stmt),
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Item::Stmt(stmt) => self.eval_stmt(stmt),
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}
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}
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}
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}
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@ -139,7 +145,7 @@ impl ExecEnv {
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}
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}
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/// Perform the action indicated by a statement.
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/// Perform the action indicated by a statement.
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fn eval_stmt(&mut self, stmt: &Stmt) -> Result<ControlFlow, Error> {
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fn eval_stmt(&mut self, stmt: &Stmt) -> Result<HaltStatus, Error> {
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match stmt {
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match stmt {
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Stmt::Print(expr) => {
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Stmt::Print(expr) => {
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println!("{}", self.eval_expr(expr)?);
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println!("{}", self.eval_expr(expr)?);
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@ -169,33 +175,33 @@ impl ExecEnv {
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Stmt::BfFDeclaration { iden: _, body: _ } => todo!(),
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Stmt::BfFDeclaration { iden: _, body: _ } => todo!(),
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Stmt::If { cond, body } => {
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Stmt::If { cond, body } => {
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if self.eval_expr(cond)?.into() {
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if self.eval_expr(cond)?.into() {
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return self.eval_items_cf(body);
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return self.eval_items_hs(body);
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}
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}
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}
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}
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Stmt::FunctionCall { iden: _, args: _ } => todo!(),
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Stmt::FunctionCall { iden: _, args: _ } => todo!(),
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Stmt::Loop { body } => loop {
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Stmt::Loop { body } => loop {
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let res = self.eval_items_cf(body)?;
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let res = self.eval_items_hs(body)?;
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match res {
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match res {
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ControlFlow::Value(_) => {}
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HaltStatus::Value(_) => {}
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ControlFlow::Break => break,
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HaltStatus::Break => break,
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ControlFlow::Hopback => continue,
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HaltStatus::Hopback => continue,
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}
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}
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},
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},
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Stmt::VarAssignment { iden, value } => {
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Stmt::VarAssignment { iden, value } => {
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self.get_var_mut(&iden.0)?.value = self.eval_expr(value)?;
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self.get_var_mut(&iden.0)?.value = self.eval_expr(value)?;
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}
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}
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Stmt::Break => {
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Stmt::Break => {
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return Ok(ControlFlow::Break);
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return Ok(HaltStatus::Break);
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}
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}
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Stmt::HopBack => {
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Stmt::HopBack => {
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return Ok(ControlFlow::Hopback);
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return Ok(HaltStatus::Hopback);
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}
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}
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Stmt::Melo(iden) => {
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Stmt::Melo(iden) => {
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self.get_var_mut(&iden.0)?.melo = true;
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self.get_var_mut(&iden.0)?.melo = true;
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}
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}
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}
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}
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Ok(ControlFlow::Value(Value::Nul))
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Ok(HaltStatus::Value(Value::Nul))
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}
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}
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/// Get a shared reference to the value of a variable. Throw an
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/// Get a shared reference to the value of a variable. Throw an
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@ -229,7 +235,8 @@ impl ExecEnv {
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/// Get a mutable reference to a variable. Throw an error if the
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/// Get a mutable reference to a variable. Throw an error if the
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/// variable is inaccessible or banned.
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/// variable is inaccessible or banned.
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fn get_var_mut(&mut self, name: &str) -> Result<&mut Variable, Error> {
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fn get_var_mut(&mut self, name: &str) -> Result<&mut Variable, Error> {
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// FIXME: This function is almost exactly the same as get_var.
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// This function is almost exactly 22 lines of duplicated code
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// from get_var, which I feel like is a bad sign...
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match self
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match self
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.stack
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.stack
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.iter_mut()
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.iter_mut()
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