town and world maps to unicode

src/transpose.rs

@@ -0,0 +1,89 @@
+pub trait TransposableIterator: Iterator {
+  fn transpose<C, J, T>(self) -> Transpose<Self>
+    where Self: Iterator<Item = C> + Clone + Sized,
+          C: IntoIterator<Item = T, IntoIter = J>,
+          J: ExactSizeIterator<Item = T>
+  {
+    Transpose::new(self)
+  }
+}
+
+impl<I> TransposableIterator for I where I: Iterator
+{}
+
+#[derive(Clone)]
+pub struct Transpose<I> {
+  loc: ::std::ops::Range<usize>,
+  iter: I,
+}
+
+impl<I, C, J, T> Transpose<I>
+  where I: Iterator<Item = C> + Clone,
+        C: IntoIterator<Item = T, IntoIter = J>,
+        J: ExactSizeIterator<Item = T>
+{
+  fn new(base: I) -> Transpose<I> {
+    let longest = base.clone()
+                      .fold(0, |len, row| ::std::cmp::max(len, row.into_iter().len()));
+
+    Transpose {
+      loc: 0..longest,
+      iter: base,
+    }
+  }
+}
+
+impl<I> Iterator for Transpose<I> where I: Clone
+{
+  type Item = TransposeInner<I>;
+
+  #[inline]
+  fn next(&mut self) -> Option<TransposeInner<I>> {
+    self.loc.next().map(|idx| {
+      TransposeInner {
+        iter: self.iter.clone(),
+        col: idx,
+      }
+    })
+  }
+
+  fn size_hint(&self) -> (usize, Option<usize>) {
+    (self.loc.end, Some(self.loc.end))
+  }
+}
+
+impl<I> ExactSizeIterator for Transpose<I> where I: Clone
+{}
+
+impl<I> DoubleEndedIterator for Transpose<I> where I: Clone
+{
+  fn next_back(&mut self) -> Option<TransposeInner<I>> {
+    self.loc.next_back().map(|idx| {
+      TransposeInner {
+        iter: self.iter.clone(),
+        col: idx,
+      }
+    })
+  }
+}
+
+#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
+#[derive(Clone)]
+pub struct TransposeInner<I> {
+  iter: I,
+  col: usize,
+}
+
+impl<I, J, T> Iterator for TransposeInner<I>
+  where I: Iterator<Item = J>,
+        J: IntoIterator<Item = T>
+{
+  type Item = T;
+
+  #[inline]
+  fn next(&mut self) -> Option<T> {
+    self.iter.next().and_then(|row| row.into_iter().nth(self.col))
+  }
+}
+
+// TODO: ExactSizeIterator and DoubleEndedIterator for TransposeInner