initial iterator object library

src/libcore/iterator.rs

@@ -0,0 +1,101 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Composable iterator objects
+
+use prelude::*;
+
+pub trait Iterator<T> {
+    /// Advance the iterator and return the next value. Return `None` when the end is reached.
+    fn next(&mut self) -> Option<T>;
+}
+
+/// A shim implementing the `for` loop iteration protocol for iterator objects
+#[inline]
+pub fn advance<T, U: Iterator<T>>(iter: &mut U, f: &fn(T) -> bool) {
+    loop {
+        match iter.next() {
+            Some(x) => {
+                if !f(x) { return }
+            }
+            None => return
+        }
+    }
+}
+
+pub struct ZipIterator<T, U> {
+    priv a: T,
+    priv b: U
+}
+
+pub impl<A, B, T: Iterator<A>, U: Iterator<B>> ZipIterator<T, U> {
+    #[inline(always)]
+    fn new(a: T, b: U) -> ZipIterator<T, U> {
+        ZipIterator{a: a, b: b}
+    }
+}
+
+impl<A, B, T: Iterator<A>, U: Iterator<B>> Iterator<(A, B)> for ZipIterator<T, U> {
+    #[inline]
+    fn next(&mut self) -> Option<(A, B)> {
+        match (self.a.next(), self.b.next()) {
+            (Some(x), Some(y)) => Some((x, y)),
+            _ => None
+        }
+    }
+}
+
+pub struct FilterIterator<'self, A, T> {
+    priv iter: T,
+    priv predicate: &'self fn(&A) -> bool
+}
+
+pub impl<'self, A, T: Iterator<A>> FilterIterator<'self, A, T> {
+    #[inline(always)]
+    fn new(iter: T, predicate: &'self fn(&A) -> bool) -> FilterIterator<'self, A, T> {
+        FilterIterator{iter: iter, predicate: predicate}
+    }
+}
+
+impl<'self, A, T: Iterator<A>> Iterator<A> for FilterIterator<'self, A, T> {
+    #[inline]
+    fn next(&mut self) -> Option<A> {
+        for advance(self) |x| {
+            if (self.predicate)(&x) {
+                return Some(x);
+            } else {
+                loop
+            }
+        }
+        None
+    }
+}
+
+pub struct MapIterator<'self, A, B, T> {
+    priv iter: T,
+    priv f: &'self fn(A) -> B
+}
+
+pub impl<'self, A, B, T: Iterator<A>> MapIterator<'self, A, B, T> {
+    #[inline(always)]
+    fn new(iter: T, f: &'self fn(A) -> B) -> MapIterator<'self, A, B, T> {
+        MapIterator{iter: iter, f: f}
+    }
+}
+
+impl<'self, A, B, T: Iterator<A>> Iterator<B> for MapIterator<'self, A, B, T> {
+    #[inline]
+    fn next(&mut self) -> Option<B> {
+        match self.iter.next() {
+            Some(a) => Some((self.f)(a)),
+            _ => None
+        }
+    }
+}