forked from AbleScript/ablescript
Clean up eval_expr
some more
I keep going back and forth on how I want this block to look :P Anyway, this is *probably* its final-ish form, until the parser gets re-written.
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d80f47716d
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98b2fae6f3
127
src/interpret.rs
127
src/interpret.rs
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@ -113,55 +113,86 @@ impl ExecEnv {
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use Expr::*;
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use Expr::*;
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use Value::*;
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use Value::*;
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// NOTE(Alex): This is really quite horrible. I think the only
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// NOTE(Alex): This block will get a whole lot cleaner once
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// real way to clean it up would be to re-engineer the AST's
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// Ondra's parser stuff gets merged (specifically 97fb19e).
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// representation to be more hierarchical: rather than having
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// For now, though, we've got a bunch of manually-checked
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// e.g. "Expr::Add" and "Expr::Subtract" each with a "left"
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// unreachable!()s in here which makes me sad...
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// and "right" struct member, have something like
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// "Expr::Binary { oper: BinOp, left: Box<Expr>, right:
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// Box<Expr> }". That way we could factor out a whole bunch of
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// common code here.
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//
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// That work should probably wait for Ondra's new parser to
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// come in, however.
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Ok(match expr {
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Ok(match expr {
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Add { left, right } => Int(i32::try_from(self.eval_expr(left)?)?
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// Binary expressions.
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.checked_add(i32::try_from(self.eval_expr(right)?)?)
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Add { left, right }
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.ok_or(Error {
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| Subtract { left, right }
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kind: ErrorKind::ArithmeticError,
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| Multiply { left, right }
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position: 0..0,
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| Divide { left, right }
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})?),
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| Lt { left, right }
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Subtract { left, right } => Int(i32::try_from(self.eval_expr(left)?)?
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| Gt { left, right }
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.checked_sub(i32::try_from(self.eval_expr(right)?)?)
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| Eq { left, right }
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.ok_or(Error {
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| Neq { left, right }
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kind: ErrorKind::ArithmeticError,
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| And { left, right }
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position: 0..0,
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| Or { left, right } => {
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})?),
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let left = self.eval_expr(left)?;
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Multiply { left, right } => Int(i32::try_from(self.eval_expr(left)?)?
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let right = self.eval_expr(right)?;
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.checked_mul(i32::try_from(self.eval_expr(right)?)?)
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.ok_or(Error {
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match expr {
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kind: ErrorKind::ArithmeticError,
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// Arithmetic operators.
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position: 0..0,
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Add { .. }
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})?),
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| Subtract { .. }
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Divide { left, right } => Int(i32::try_from(self.eval_expr(left)?)?
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| Multiply { .. }
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.checked_div(i32::try_from(self.eval_expr(right)?)?)
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| Divide { .. } => {
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.ok_or(Error {
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let left = i32::try_from(left)?;
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kind: ErrorKind::ArithmeticError,
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let right = i32::try_from(right)?;
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position: 0..0,
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})?),
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let res = match expr {
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Lt { left, right } => {
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Add { .. } => left.checked_add(right),
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Bool(i32::try_from(self.eval_expr(left)?)? < i32::try_from(self.eval_expr(right)?)?)
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Subtract { .. } => left.checked_sub(right),
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}
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Multiply { .. } => left.checked_mul(right),
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Gt { left, right } => {
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Divide { .. } => left.checked_div(right),
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Bool(i32::try_from(self.eval_expr(left)?)? > i32::try_from(self.eval_expr(right)?)?)
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_ => unreachable!(),
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}
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}
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Eq { left, right } => Bool(self.eval_expr(left)? == self.eval_expr(right)?),
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.ok_or(Error {
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Neq { left, right } => Bool(self.eval_expr(left)? != self.eval_expr(right)?),
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kind: ErrorKind::ArithmeticError,
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And { left, right } => {
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position: 0..0,
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Bool(bool::from(self.eval_expr(left)?) && bool::from(self.eval_expr(right)?))
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})?;
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}
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Int(res)
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Or { left, right } => {
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}
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Bool(bool::from(self.eval_expr(left)?) || bool::from(self.eval_expr(right)?))
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// Numeric comparisons.
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Lt { .. } | Gt { .. } => {
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let left = i32::try_from(left)?;
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let right = i32::try_from(right)?;
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let res = match expr {
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Lt { .. } => left < right,
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Gt { .. } => left > right,
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_ => unreachable!(),
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};
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Bool(res)
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}
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// General comparisons.
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Eq { .. } | Neq { .. } => {
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let res = match expr {
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Eq { .. } => left == right,
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Neq { .. } => left != right,
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_ => unreachable!(),
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};
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Bool(res)
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}
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// Logical connectives.
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And { .. } | Or { .. } => {
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let left = bool::from(left);
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let right = bool::from(right);
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let res = match expr {
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And { .. } => left && right,
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Or { .. } => left || right,
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_ => unreachable!(),
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};
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Bool(res)
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}
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// That's all the binary operations.
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_ => unreachable!(),
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}
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}
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}
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Not(expr) => Bool(!bool::from(self.eval_expr(expr)?)),
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Not(expr) => Bool(!bool::from(self.eval_expr(expr)?)),
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Literal(value) => value.clone(),
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Literal(value) => value.clone(),
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