Use slice::iter instead of into_iter to avoid future breakage

`an_array.into_iter()` currently just works because of the autoref
feature, which then calls `<[T] as IntoIterator>::into_iter`. But
in the future, arrays will implement `IntoIterator`, too. In order
to avoid problems in the future, the call is replaced by `iter()`
which is shorter and more explicit.

src/eval.rs

@@ -569,7 +569,7 @@ impl Context {
                 value = rem;
             }
         }
-        Ok(list.into_iter().zip(out.into_iter()).map(|(name, value)| {
+        Ok(list.iter().zip(out.into_iter()).map(|(name, value)| {
             let pretty = Number {
                 value: value,
                 unit: Number::one_unit(Dim::new(name)).unit

src/factorize.rs

@@ -38,7 +38,7 @@ pub fn fast_decompose(value: &Number, quantities: &BTreeMap<Unit, String>) -> Un
             value: Num::one(),
             unit: unit.clone(),
         };
-        for &i in [-1, 1, 2].into_iter() {
+        for &i in [-1, 1, 2].iter() {
             let res = (value / &num.powi(i)).unwrap();
             let score = res.complexity_score();
             let better = best.as_ref().map(|&(_, _, _, current)| score < current).unwrap_or(true);