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Fix copy paste error, better errors

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This commit is contained in:
Tiffany Bennett 2016-08-11 22:07:21 -04:00
parent f33b445f32
commit ce1474fd7b
1 changed files with 17 additions and 8 deletions
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25
src/eval.rs
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@ -215,6 +215,17 @@ impl Context {
pub fn eval(&self, expr: &::unit_defs::Expr) -> Result<Value, String> {
use unit_defs::Expr;
macro_rules! operator {
($left:ident $op:ident $opname:tt $right:ident) => {{
let left = try!(self.eval(&**$left));
let right = try!(self.eval(&**$right));
((&left).$op(&right)).map_err(|e| {
format!("{}: <{}> {} <{}>",
e, left.show(self), stringify!($opname), right.show(self))
})
}}
}
match *expr {
Expr::Unit(ref name) => self.lookup(name).ok_or(format!("Unknown unit {}", name)).map(Value::Number),
Expr::Const(ref num, ref frac, ref exp) =>
@ -226,12 +237,12 @@ impl Context {
Expr::Date(ref date) => date::try_decode(date, self).map(Value::DateTime),
Expr::Neg(ref expr) => self.eval(&**expr).and_then(|v| -&v),
Expr::Plus(ref expr) => self.eval(&**expr),
Expr::Frac(ref top, ref bottom) =>
&try!(self.eval(&**top)) / &try!(self.eval(&**bottom)),
Expr::Add(ref top, ref bottom) =>
&try!(self.eval(&**top)) / &try!(self.eval(&**bottom)),
Expr::Sub(ref top, ref bottom) =>
&try!(self.eval(&**top)) / &try!(self.eval(&**bottom)),
Expr::Frac(ref left, ref right) => operator!(left div / right),
Expr::Add(ref left, ref right) => operator!(left add + right),
Expr::Sub(ref left, ref right) => operator!(left sub - right),
Expr::Pow(ref left, ref right) => operator!(left pow ^ right),
// TODO: A type might not implement * on Number, and this would fail
Expr::Mul(ref args) => args.iter().fold(Ok(Value::Number(Number::one())), |a, b| {
a.and_then(|a| {
@ -239,8 +250,6 @@ impl Context {
Ok((&a * &b).unwrap())
})
}),
Expr::Pow(ref base, ref exp) =>
try!(self.eval(&**base)).pow(&try!(self.eval(&**exp))),
Expr::Convert(_, _) => Err(format!("Conversions (->) must be top-level expressions")),
Expr::Error(ref e) => Err(e.clone()),
}