Specialize Enumerable#max and Enumerable#min for Range

This patch prevents a hang for pathalogical (large) Ranges when
computing max and min.

Range inherits its implementation of max and min from Enumerable.
Enumerable implements max and min by calling each. For Range objects,
this is unnecessary since we know the max and the min by the end and
begin attributes.

It is also very slow. This code hangs unnecessarily:

    (0..2**32).max
    # ... hang
    (0..2**32).min
    # ... hang

This patch overrides max and min after including enumerable to yield
based on the begin and end methods.

1 files changed, 65 insertions, 1 deletions

diff --git a/mrblib/range.rb b/mrblib/range.rb
index 392cc2274..746cb322c 100644
--- a/mrblib/range.rb
+++ b/mrblib/range.rb
@@ -15,7 +15,8 @@ class Range
     val = self.first
     last = self.last
 
-    if val.kind_of?(Fixnum) && last.kind_of?(Fixnum) # fixnums are special
+    # numerics are special
+    if (val.kind_of?(Fixnum) || val.kind_of?(Float)) && (last.kind_of?(Fixnum) || last.kind_of?(Float))
       lim = last
       lim += 1 unless exclude_end?
       i = val
@@ -64,4 +65,67 @@ end
 # ISO 15.2.14.3
 class Range
   include Enumerable
+
+  def max(&block)
+    val = self.first
+    last = self.last
+    # numerics are special
+    if (val.kind_of?(Fixnum) || val.kind_of?(Float)) && (last.kind_of?(Fixnum) || last.kind_of?(Float))
+      return nil if val > last
+      return nil if val == last && exclude_end?
+
+      max = last
+      max -= 1 if exclude_end?
+      max = val if block && block.call(val, last) > 0
+      return max
+    end
+
+    max = nil
+    each do |item|
+      max =
+        if max.nil?
+          item
+        elsif block && block.call(max, item) > 0
+          item
+        elsif item > max
+          item
+        else
+          max
+        end
+    end
+    max
+  end
+
+  def min(&block)
+    val = self.first
+    last = self.last
+
+    # numerics are special
+    if (val.kind_of?(Fixnum) || val.kind_of?(Float)) && (last.kind_of?(Fixnum) || last.kind_of?(Float))
+      return nil if val > last
+      return nil if val == last && exclude_end?
+
+      min = val
+      if block && block.call(val, last) > 0
+        min = last
+        min -= 1 if exclude_end?
+      end
+      return min
+    end
+
+    min = nil
+    each do |item|
+      min =
+        if min.nil?
+          item
+        elsif block && block.call(min, item) < 0
+          item
+        elsif item < min
+          item
+        else
+          min
+        end
+    end
+    min
+  end
 end