auto merge of #7684 : pnkfelix/rust/fsk-invert-range-rev-halfclosedness-issue5270-2ndpr, r=cmr

Changes int/uint range_rev to iterate over range `(hi,lo]` instead of `[hi,lo)`.

Fix #5270.

Also:
* Adds unit tests for int/uint range functions
* Updates the uses of `range_rev` to account for the new semantics.  (Note that pretty much all of the updates there were strict improvements to the code in question; yay!)
* Exposes new function, `range_step_inclusive`, which does the range `[hi,lo]`, (at least when `hi-lo` is a multiple of the `step` parameter).
* Special-cases when `|step| == 1` removing unnecessary bounds-check.  (I did not check whether LLVM was already performing this optimization; I figure it would be a net win to not leave that analysis to the compiler.  If reviewer objects, I can easily remove that from the refactored code.)

(This pull request is a rebased version of PR #7524, which went stale due to recent unrelated changes to num libraries.)

Author: bors

src/libextra/smallintmap.rs

@@ -161,8 +161,8 @@ impl<V> SmallIntMap<V> {
     /// Visit all key-value pairs in reverse order
     pub fn each_reverse<'a>(&'a self, it: &fn(uint, &'a V) -> bool) -> bool {
         for uint::range_rev(self.v.len(), 0) |i| {
-            match self.v[i - 1] {
-              Some(ref elt) => if !it(i - 1, elt) { return false; },
+            match self.v[i] {
+              Some(ref elt) => if !it(i, elt) { return false; },
               None => ()
             }
         }

src/libstd/num/int_macros.rs

@@ -29,28 +29,38 @@ pub static bytes : uint = ($bits / 8);
 pub static min_value: $T = (-1 as $T) << (bits - 1);
 pub static max_value: $T = min_value - 1 as $T;
 
+enum Range { Closed, HalfOpen }
+
+#[inline]
 ///
-/// Iterate over the range [`lo`..`hi`)
+/// Iterate through a range with a given step value.
 ///
-/// # Arguments
+/// Let `term` denote the closed interval `[stop-step,stop]` if `r` is Closed;
+/// otherwise `term` denotes the half-open interval `[stop-step,stop)`.
+/// Iterates through the range `[x_0, x_1, ..., x_n]` where
+/// `x_j == start + step*j`, and `x_n` lies in the interval `term`.
 ///
-/// * `lo` - lower bound, inclusive
-/// * `hi` - higher bound, exclusive
-///
-/// # Examples
-/// ~~~
-/// let mut sum = 0;
-/// for int::range(1, 5) |i| {
-///     sum += i;
-/// }
-/// assert!(sum == 10);
-/// ~~~
+/// If no such nonnegative integer `n` exists, then the iteration range
+/// is empty.
 ///
-#[inline]
-pub fn range_step(start: $T, stop: $T, step: $T, it: &fn($T) -> bool) -> bool {
+fn range_step_core(start: $T, stop: $T, step: $T, r: Range, it: &fn($T) -> bool) -> bool {
     let mut i = start;
     if step == 0 {
         fail!(~"range_step called with step == 0");
+    } else if step == (1 as $T) { // elide bounds check to tighten loop
+        while i < stop {
+            if !it(i) { return false; }
+            // no need for overflow check;
+            // cannot have i + 1 > max_value because i < stop <= max_value
+            i += (1 as $T);
+        }
+    } else if step == (-1 as $T) { // elide bounds check to tighten loop
+        while i > stop {
+            if !it(i) { return false; }
+            // no need for underflow check;
+            // cannot have i - 1 < min_value because i > stop >= min_value
+            i -= (1 as $T);
+        }
     } else if step > 0 { // ascending
         while i < stop {
             if !it(i) { return false; }
@@ -66,19 +76,66 @@ pub fn range_step(start: $T, stop: $T, step: $T, it: &fn($T) -> bool) -> bool {
             i += step;
         }
     }
-    return true;
+    match r {
+        HalfOpen => return true,
+        Closed => return (i != stop || it(i))
+    }
+}
+
+#[inline]
+///
+/// Iterate through the range [`start`..`stop`) with a given step value.
+///
+/// Iterates through the range `[x_0, x_1, ..., x_n]` where
+/// * `x_i == start + step*i`, and
+/// * `n` is the greatest nonnegative integer such that `x_n < stop`
+///
+/// (If no such `n` exists, then the iteration range is empty.)
+///
+/// # Arguments
+///
+/// * `start` - lower bound, inclusive
+/// * `stop` - higher bound, exclusive
+///
+/// # Examples
+/// ~~~
+/// let mut sum = 0;
+/// for int::range(1, 5) |i| {
+///     sum += i;
+/// }
+/// assert!(sum == 10);
+/// ~~~
+///
+pub fn range_step(start: $T, stop: $T, step: $T, it: &fn($T) -> bool) -> bool {
+    range_step_core(start, stop, step, HalfOpen, it)
+}
+
+#[inline]
+///
+/// Iterate through a range with a given step value.
+///
+/// Iterates through the range `[x_0, x_1, ..., x_n]` where
+/// `x_i == start + step*i` and `x_n <= last < step + x_n`.
+///
+/// (If no such nonnegative integer `n` exists, then the iteration
+///  range is empty.)
+///
+pub fn range_step_inclusive(start: $T, last: $T, step: $T, it: &fn($T) -> bool) -> bool {
+    range_step_core(start, last, step, Closed, it)
 }
 
+
 #[inline]
 /// Iterate over the range [`lo`..`hi`)
 pub fn range(lo: $T, hi: $T, it: &fn($T) -> bool) -> bool {
     range_step(lo, hi, 1 as $T, it)
 }
 
 #[inline]
-/// Iterate over the range [`hi`..`lo`)
+/// Iterate over the range (`hi`..`lo`]
 pub fn range_rev(hi: $T, lo: $T, it: &fn($T) -> bool) -> bool {
-    range_step(hi, lo, -1 as $T, it)
+    if hi == min_value { return true; }
+    range_step_inclusive(hi-1, lo, -1 as $T, it)
 }
 
 impl Num for $T {}
@@ -841,7 +898,7 @@ mod tests {
         for range(0,3) |i| {
             l.push(i);
         }
-        for range_rev(13,10) |i| {
+        for range_rev(14,11) |i| {
             l.push(i);
         }
         for range_step(20,26,2) |i| {

src/libstd/num/uint_macros.rs

@@ -30,40 +30,99 @@ pub static bytes : uint = ($bits / 8);
 pub static min_value: $T = 0 as $T;
 pub static max_value: $T = 0 as $T - 1 as $T;
 
+enum Range { Closed, HalfOpen }
+
 #[inline]
-/**
- * Iterate through a range with a given step value.
- *
- * # Examples
- * ~~~ {.rust}
- * let nums = [1,2,3,4,5,6,7];
- *
- * for uint::range_step(0, nums.len() - 1, 2) |i| {
- *     println(fmt!("%d & %d", nums[i], nums[i+1]));
- * }
- * ~~~
- */
-pub fn range_step(start: $T, stop: $T, step: $T_SIGNED, it: &fn($T) -> bool) -> bool {
+///
+/// Iterate through a range with a given step value.
+///
+/// Let `term` denote the closed interval `[stop-step,stop]` if `r` is Closed;
+/// otherwise `term` denotes the half-open interval `[stop-step,stop)`.
+/// Iterates through the range `[x_0, x_1, ..., x_n]` where
+/// `x_j == start + step*j`, and `x_n` lies in the interval `term`.
+///
+/// If no such nonnegative integer `n` exists, then the iteration range
+/// is empty.
+///
+fn range_step_core(start: $T, stop: $T, step: $T_SIGNED, r: Range, it: &fn($T) -> bool) -> bool {
     let mut i = start;
     if step == 0 {
         fail!("range_step called with step == 0");
-    }
-    if step >= 0 {
+    } else if step == (1 as $T_SIGNED) { // elide bounds check to tighten loop
+        while i < stop {
+            if !it(i) { return false; }
+            // no need for overflow check;
+            // cannot have i + 1 > max_value because i < stop <= max_value
+            i += (1 as $T);
+        }
+    } else if step == (-1 as $T_SIGNED) { // elide bounds check to tighten loop
+        while i > stop {
+            if !it(i) { return false; }
+            // no need for underflow check;
+            // cannot have i - 1 < min_value because i > stop >= min_value
+            i -= (1 as $T);
+        }
+    } else if step > 0 { // ascending
         while i < stop {
             if !it(i) { return false; }
             // avoiding overflow. break if i + step > max_value
             if i > max_value - (step as $T) { return true; }
             i += step as $T;
         }
-    } else {
+    } else { // descending
         while i > stop {
             if !it(i) { return false; }
             // avoiding underflow. break if i + step < min_value
             if i < min_value + ((-step) as $T) { return true; }
             i -= -step as $T;
         }
     }
-    return true;
+    match r {
+        HalfOpen => return true,
+        Closed => return (i != stop || it(i))
+    }
+}
+
+#[inline]
+///
+/// Iterate through the range [`start`..`stop`) with a given step value.
+///
+/// Iterates through the range `[x_0, x_1, ..., x_n]` where
+/// - `x_i == start + step*i`, and
+/// - `n` is the greatest nonnegative integer such that `x_n < stop`
+///
+/// (If no such `n` exists, then the iteration range is empty.)
+///
+/// # Arguments
+///
+/// * `start` - lower bound, inclusive
+/// * `stop` - higher bound, exclusive
+///
+/// # Examples
+/// ~~~ {.rust}
+/// let nums = [1,2,3,4,5,6,7];
+///
+/// for uint::range_step(0, nums.len() - 1, 2) |i| {
+///     println(fmt!("%d & %d", nums[i], nums[i+1]));
+/// }
+/// ~~~
+///
+pub fn range_step(start: $T, stop: $T, step: $T_SIGNED, it: &fn($T) -> bool) -> bool {
+    range_step_core(start, stop, step, HalfOpen, it)
+}
+
+#[inline]
+///
+/// Iterate through a range with a given step value.
+///
+/// Iterates through the range `[x_0, x_1, ..., x_n]` where
+/// `x_i == start + step*i` and `x_n <= last < step + x_n`.
+///
+/// (If no such nonnegative integer `n` exists, then the iteration
+///  range is empty.)
+///
+pub fn range_step_inclusive(start: $T, last: $T, step: $T_SIGNED, it: &fn($T) -> bool) -> bool {
+    range_step_core(start, last, step, Closed, it)
 }
 
 #[inline]
@@ -73,9 +132,10 @@ pub fn range(lo: $T, hi: $T, it: &fn($T) -> bool) -> bool {
 }
 
 #[inline]
-/// Iterate over the range [`hi`..`lo`)
+/// Iterate over the range (`hi`..`lo`]
 pub fn range_rev(hi: $T, lo: $T, it: &fn($T) -> bool) -> bool {
-    range_step(hi, lo, -1 as $T_SIGNED, it)
+    if hi == min_value { return true; }
+    range_step_inclusive(hi-1, lo, -1 as $T_SIGNED, it)
 }
 
 impl Num for $T {}
@@ -603,7 +663,7 @@ mod tests {
         for range(0,3) |i| {
             l.push(i);
         }
-        for range_rev(13,10) |i| {
+        for range_rev(14,11) |i| {
             l.push(i);
         }
         for range_step(20,26,2) |i| {

src/libstd/run.rs

@@ -669,7 +669,7 @@ fn spawn_process_os(prog: &str, args: &[~str],
             fail!("failure in dup3(err_fd, 2): %s", os::last_os_error());
         }
         // close all other fds
-        for int::range_rev(getdtablesize() as int - 1, 2) |fd| {
+        for int::range_rev(getdtablesize() as int, 3) |fd| {
             close(fd as c_int);
         }
 

src/libstd/trie.rs

@@ -287,7 +287,7 @@ impl<T> TrieNode<T> {
 
     fn each_reverse<'a>(&'a self, f: &fn(&uint, &'a T) -> bool) -> bool {
         for uint::range_rev(self.children.len(), 0) |idx| {
-            match self.children[idx - 1] {
+            match self.children[idx] {
                 Internal(ref x) => if !x.each_reverse(|i,t| f(i,t)) { return false },
                 External(k, ref v) => if !f(&k, v) { return false },
                 Nothing => ()
@@ -488,7 +488,7 @@ mod test_map {
             m.insert(x, x / 2);
         }
 
-        let mut n = uint::max_value - 9999;
+        let mut n = uint::max_value - 10000;
         for m.each |k, v| {
             if n == uint::max_value - 5000 { break }
             assert!(n < uint::max_value - 5000);
@@ -525,7 +525,7 @@ mod test_map {
             m.insert(x, x / 2);
         }
 
-        let mut n = uint::max_value;
+        let mut n = uint::max_value - 1;
         for m.each_reverse |k, v| {
             if n == uint::max_value - 5000 { break }
             assert!(n > uint::max_value - 5000);