Add `iter` modules for generic number iteration.

The codes are imported from the standard library.

src/iter.rs

@@ -0,0 +1,341 @@
+// Copyright 2013-2014 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.
+
+//! External iterators for generic mathematics
+
+use {Integer, Zero, One, CheckedAdd};
+use std::num::Int;
+
+/// An iterator over the range [start, stop)
+#[deriving(Clone)]
+pub struct Range<A> {
+    state: A,
+    stop: A,
+    one: A
+}
+
+/// Returns an iterator over the given range [start, stop) (that is, starting
+/// at start (inclusive), and ending at stop (exclusive)).
+///
+/// # Example
+///
+/// ```rust
+/// let array = [0, 1, 2, 3, 4];
+///
+/// for i in range(0, 5u) {
+///     println!("{}", i);
+///     assert_eq!(i,  array[i]);
+/// }
+/// ```
+#[inline]
+pub fn range<A: Add<A, A> + PartialOrd + Clone + One>(start: A, stop: A) -> Range<A> {
+    Range{state: start, stop: stop, one: One::one()}
+}
+
+// FIXME: rust-lang/rust#10414: Unfortunate type bound
+impl<A: Add<A, A> + PartialOrd + Clone + ToPrimitive> Iterator<A> for Range<A> {
+    #[inline]
+    fn next(&mut self) -> Option<A> {
+        if self.state < self.stop {
+            let result = self.state.clone();
+            self.state = self.state + self.one;
+            Some(result)
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (uint, Option<uint>) {
+        // This first checks if the elements are representable as i64. If they aren't, try u64 (to
+        // handle cases like range(huge, huger)). We don't use uint/int because the difference of
+        // the i64/u64 might lie within their range.
+        let bound = match self.state.to_i64() {
+            Some(a) => {
+                let sz = self.stop.to_i64().map(|b| b.checked_sub(a));
+                match sz {
+                    Some(Some(bound)) => bound.to_uint(),
+                    _ => None,
+                }
+            },
+            None => match self.state.to_u64() {
+                Some(a) => {
+                    let sz = self.stop.to_u64().map(|b| b.checked_sub(a));
+                    match sz {
+                        Some(Some(bound)) => bound.to_uint(),
+                        _ => None
+                    }
+                },
+                None => None
+            }
+        };
+
+        match bound {
+            Some(b) => (b, Some(b)),
+            // Standard fallback for unbounded/unrepresentable bounds
+            None => (0, None)
+        }
+    }
+}
+
+/// `Integer` is required to ensure the range will be the same regardless of
+/// the direction it is consumed.
+impl<A: Integer + PartialOrd + Clone + ToPrimitive> DoubleEndedIterator<A> for Range<A> {
+    #[inline]
+    fn next_back(&mut self) -> Option<A> {
+        if self.stop > self.state {
+            self.stop = self.stop - self.one;
+            Some(self.stop.clone())
+        } else {
+            None
+        }
+    }
+}
+
+/// An iterator over the range [start, stop]
+#[deriving(Clone)]
+pub struct RangeInclusive<A> {
+    range: Range<A>,
+    done: bool,
+}
+
+/// Return an iterator over the range [start, stop]
+#[inline]
+pub fn range_inclusive<A: Add<A, A> + PartialOrd + Clone + One>(start: A, stop: A)
+    -> RangeInclusive<A> {
+    RangeInclusive{range: range(start, stop), done: false}
+}
+
+impl<A: Add<A, A> + PartialOrd + Clone + ToPrimitive> Iterator<A> for RangeInclusive<A> {
+    #[inline]
+    fn next(&mut self) -> Option<A> {
+        match self.range.next() {
+            Some(x) => Some(x),
+            None => {
+                if !self.done && self.range.state == self.range.stop {
+                    self.done = true;
+                    Some(self.range.stop.clone())
+                } else {
+                    None
+                }
+            }
+        }
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (uint, Option<uint>) {
+        let (lo, hi) = self.range.size_hint();
+        if self.done {
+            (lo, hi)
+        } else {
+            let lo = lo.saturating_add(1);
+            let hi = match hi {
+                Some(x) => x.checked_add(1),
+                None => None
+            };
+            (lo, hi)
+        }
+    }
+}
+
+impl<A: Sub<A, A> + Integer + PartialOrd + Clone + ToPrimitive> DoubleEndedIterator<A>
+    for RangeInclusive<A> {
+    #[inline]
+    fn next_back(&mut self) -> Option<A> {
+        if self.range.stop > self.range.state {
+            let result = self.range.stop.clone();
+            self.range.stop = self.range.stop - self.range.one;
+            Some(result)
+        } else if !self.done && self.range.state == self.range.stop {
+            self.done = true;
+            Some(self.range.stop.clone())
+        } else {
+            None
+        }
+    }
+}
+
+/// An iterator over the range [start, stop) by `step`. It handles overflow by stopping.
+#[deriving(Clone)]
+pub struct RangeStep<A> {
+    state: A,
+    stop: A,
+    step: A,
+    rev: bool,
+}
+
+/// Return an iterator over the range [start, stop) by `step`. It handles overflow by stopping.
+#[inline]
+pub fn range_step<A: CheckedAdd + PartialOrd +
+                  Clone + Zero>(start: A, stop: A, step: A) -> RangeStep<A> {
+    let rev = step < Zero::zero();
+    RangeStep{state: start, stop: stop, step: step, rev: rev}
+}
+
+impl<A: CheckedAdd + PartialOrd + Clone> Iterator<A> for RangeStep<A> {
+    #[inline]
+    fn next(&mut self) -> Option<A> {
+        if (self.rev && self.state > self.stop) || (!self.rev && self.state < self.stop) {
+            let result = self.state.clone();
+            match self.state.checked_add(&self.step) {
+                Some(x) => self.state = x,
+                None => self.state = self.stop.clone()
+            }
+            Some(result)
+        } else {
+            None
+        }
+    }
+}
+
+/// An iterator over the range [start, stop] by `step`. It handles overflow by stopping.
+#[deriving(Clone)]
+pub struct RangeStepInclusive<A> {
+    state: A,
+    stop: A,
+    step: A,
+    rev: bool,
+    done: bool,
+}
+
+/// Return an iterator over the range [start, stop] by `step`. It handles overflow by stopping.
+#[inline]
+pub fn range_step_inclusive<A: CheckedAdd + PartialOrd + Clone + Zero>(start: A, stop: A,
+                                                                step: A) -> RangeStepInclusive<A> {
+    let rev = step < Zero::zero();
+    RangeStepInclusive{state: start, stop: stop, step: step, rev: rev, done: false}
+}
+
+impl<A: CheckedAdd + PartialOrd + Clone + PartialEq> Iterator<A> for RangeStepInclusive<A> {
+    #[inline]
+    fn next(&mut self) -> Option<A> {
+        if !self.done && ((self.rev && self.state >= self.stop) ||
+                          (!self.rev && self.state <= self.stop)) {
+            let result = self.state.clone();
+            match self.state.checked_add(&self.step) {
+                Some(x) => self.state = x,
+                None => self.done = true
+            }
+            Some(result)
+        } else {
+            None
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::uint;
+    use One;
+
+    #[test]
+    fn test_range() {
+        /// A mock type to check Range when ToPrimitive returns None
+        struct Foo;
+
+        impl ToPrimitive for Foo {
+            fn to_i64(&self) -> Option<i64> { None }
+            fn to_u64(&self) -> Option<u64> { None }
+        }
+
+        impl Add<Foo, Foo> for Foo {
+            fn add(&self, _: &Foo) -> Foo {
+                Foo
+            }
+        }
+
+        impl PartialEq for Foo {
+            fn eq(&self, _: &Foo) -> bool {
+                true
+            }
+        }
+
+        impl PartialOrd for Foo {
+            fn partial_cmp(&self, _: &Foo) -> Option<Ordering> {
+                None
+            }
+        }
+
+        impl Clone for Foo {
+            fn clone(&self) -> Foo {
+                Foo
+            }
+        }
+
+        impl Mul<Foo, Foo> for Foo {
+            fn mul(&self, _: &Foo) -> Foo {
+                Foo
+            }
+        }
+
+        impl One for Foo {
+            fn one() -> Foo {
+                Foo
+            }
+        }
+
+        assert!(super::range(0i, 5).collect::<Vec<int>>() == vec![0i, 1, 2, 3, 4]);
+        assert!(super::range(-10i, -1).collect::<Vec<int>>() ==
+                vec![-10, -9, -8, -7, -6, -5, -4, -3, -2]);
+        assert!(super::range(0i, 5).rev().collect::<Vec<int>>() == vec![4, 3, 2, 1, 0]);
+        assert_eq!(super::range(200i, -5).count(), 0);
+        assert_eq!(super::range(200i, -5).rev().count(), 0);
+        assert_eq!(super::range(200i, 200).count(), 0);
+        assert_eq!(super::range(200i, 200).rev().count(), 0);
+
+        assert_eq!(super::range(0i, 100).size_hint(), (100, Some(100)));
+        // this test is only meaningful when sizeof uint < sizeof u64
+        assert_eq!(super::range(uint::MAX - 1, uint::MAX).size_hint(), (1, Some(1)));
+        assert_eq!(super::range(-10i, -1).size_hint(), (9, Some(9)));
+        assert_eq!(super::range(Foo, Foo).size_hint(), (0, None));
+    }
+
+    #[test]
+    fn test_range_inclusive() {
+        assert!(super::range_inclusive(0i, 5).collect::<Vec<int>>() ==
+                vec![0i, 1, 2, 3, 4, 5]);
+        assert!(super::range_inclusive(0i, 5).rev().collect::<Vec<int>>() ==
+                vec![5i, 4, 3, 2, 1, 0]);
+        assert_eq!(super::range_inclusive(200i, -5).count(), 0);
+        assert_eq!(super::range_inclusive(200i, -5).rev().count(), 0);
+        assert!(super::range_inclusive(200i, 200).collect::<Vec<int>>() == vec![200]);
+        assert!(super::range_inclusive(200i, 200).rev().collect::<Vec<int>>() == vec![200]);
+    }
+
+    #[test]
+    fn test_range_step() {
+        assert!(super::range_step(0i, 20, 5).collect::<Vec<int>>() ==
+                vec![0, 5, 10, 15]);
+        assert!(super::range_step(20i, 0, -5).collect::<Vec<int>>() ==
+                vec![20, 15, 10, 5]);
+        assert!(super::range_step(20i, 0, -6).collect::<Vec<int>>() ==
+                vec![20, 14, 8, 2]);
+        assert!(super::range_step(200u8, 255, 50).collect::<Vec<u8>>() ==
+                vec![200u8, 250]);
+        assert!(super::range_step(200i, -5, 1).collect::<Vec<int>>() == vec![]);
+        assert!(super::range_step(200i, 200, 1).collect::<Vec<int>>() == vec![]);
+    }
+
+    #[test]
+    fn test_range_step_inclusive() {
+        assert!(super::range_step_inclusive(0i, 20, 5).collect::<Vec<int>>() ==
+                vec![0, 5, 10, 15, 20]);
+        assert!(super::range_step_inclusive(20i, 0, -5).collect::<Vec<int>>() ==
+                vec![20, 15, 10, 5, 0]);
+        assert!(super::range_step_inclusive(20i, 0, -6).collect::<Vec<int>>() ==
+                vec![20, 14, 8, 2]);
+        assert!(super::range_step_inclusive(200u8, 255, 50).collect::<Vec<u8>>() ==
+                vec![200u8, 250]);
+        assert!(super::range_step_inclusive(200i, -5, 1).collect::<Vec<int>>() ==
+                vec![]);
+        assert!(super::range_step_inclusive(200i, 200, 1).collect::<Vec<int>>() ==
+                vec![200]);
+    }
+}

src/lib.rs

@@ -64,12 +64,14 @@ pub use bigint::{BigInt, BigUint};
 pub use rational::{Rational, BigRational};
 pub use complex::Complex;
 pub use integer::Integer;
+pub use iter::{range, range_inclusive, range_step, range_step_inclusive};
 pub use traits::{Num, Zero, One, Signed, Unsigned, Bounded,
                  Saturating, CheckedAdd, CheckedSub, CheckedMul, CheckedDiv};
 
 pub mod bigint;
 pub mod complex;
 pub mod integer;
+pub mod iter;
 pub mod traits;
 pub mod rational;