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Allow roots

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This commit is contained in:
Tiffany Bennett 2016-08-02 23:44:02 -04:00
parent 57b8674edc
commit ba948c7ae8
1 changed files with 17 additions and 3 deletions
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20
src/eval.rs
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@ -80,6 +80,18 @@ impl Value {
.map(|(&k, &power)| (k, power * exp as i64))
.collect::<Unit>())
}
pub fn root(&self, exp: i32) -> Option<Value> {
let mut res = Unit::new();
for (&dim, &power) in &self.1 {
if power % exp as i64 != 0 {
return None
} else {
res.insert(dim, power / exp as i64);
}
}
Some(Value(self.0.powf(1.0 / exp as f64), res))
}
}
impl Context {
@ -170,10 +182,12 @@ impl Context {
let exp = try!(self.eval(&**exp));
if exp.1.len() != 0 {
Err(format!("Exponent not dimensionless"))
} else if exp.0.trunc() != exp.0 {
Err(format!("Exponent not integer"))
} else {
} else if exp.0.trunc() == exp.0 {
Ok(base.pow(exp.0 as i32))
} else if (1.0 / exp.0).trunc() == 1.0 / exp.0 {
base.root((1.0 / exp.0) as i32).ok_or(format!("Unit roots must result in integer dimensions"))
} else {
Err(format!("Exponent not integer"))
}
},
Expr::Error(ref e) => Err(e.clone()),