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Add btree_merge()

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Tiffany Bennett 2016-08-07 13:44:52 -04:00
parent 1b5e0a8ac9
commit 3307273ce7
1 changed files with 39 additions and 38 deletions
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77
src/eval.rs
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@ -118,6 +118,44 @@ fn to_string(rational: &Mpq) -> (bool, String) {
}
}
fn btree_merge<K: ::std::cmp::Ord+Clone, V:Clone, F:Fn(&V, &V) -> Option<V>>(
left: &BTreeMap<K, V>, right: &BTreeMap<K, V>, merge_func: F
) -> BTreeMap<K, V> {
let mut res = BTreeMap::new();
let mut a = left.iter().peekable();
let mut b = right.iter().peekable();
loop {
match (a.peek().cloned(), b.peek().cloned()) {
(Some((akey, aval)), Some((bkey, bval))) if akey == bkey => {
if let Some(v) = merge_func(aval, bval) {
res.insert(akey.clone(), v);
}
a.next();
b.next();
},
(Some((akey, _)), Some((bkey, bval))) if akey > bkey => {
res.insert(bkey.clone(), bval.clone());
b.next();
},
(Some((akey, aval)), Some((bkey, _))) if akey < bkey => {
res.insert(akey.clone(), aval.clone());
a.next();
},
(Some(_), Some(_)) => panic!(),
(None, Some((bkey, bval))) => {
res.insert(bkey.clone(), bval.clone());
b.next();
},
(Some((akey, aval)), None) => {
res.insert(akey.clone(), aval.clone());
a.next();
},
(None, None) => break,
}
}
res
}
impl Value {
/// Creates a dimensionless value.
pub fn new(num: Num) -> Value {
@ -149,44 +187,7 @@ impl Value {
/// Multiplies two values, also multiplying their units.
pub fn mul(&self, other: &Value) -> Value {
let mut val = Unit::new();
let mut a = self.1.iter().peekable();
let mut b = other.1.iter().peekable();
loop {
match (a.peek().cloned(), b.peek().cloned()) {
(Some((ka, pa)), Some((kb, pb))) if ka == kb => {
// merge
let power = pa+pb;
if power != 0 {
val.insert(ka.clone(), power);
}
a.next();
b.next();
},
(Some((ka, _)), Some((kb, vb))) if ka > kb => {
// push vb, advance
val.insert(kb.clone(), vb.clone());
b.next();
},
(Some((ka, va)), Some((kb, _))) if ka < kb => {
// push va, advance
val.insert(ka.clone(), va.clone());
a.next();
},
(Some(_), Some(_)) => panic!(),
(None, Some((kb, vb))) => {
// push vb, advance
val.insert(kb.clone(), vb.clone());
b.next();
},
(Some((ka, va)), None) => {
// push va, advance
val.insert(ka.clone(), va.clone());
a.next();
},
(None, None) => break
}
}
let val = btree_merge(&self.1, &other.1, |a, b| if a+b != 0 { Some(a + b) } else { None });
Value(&self.0 * &other.0, val)
}