irange: introduce one-parameter variant of irange

this simplifies the use of boost::irange, as boost::irange( 0, foo );
may compile or not depending on the platform-specific integer type of
foo, requiring an explicit cast of 0 to decltype(foo).

doc/reference/ranges/irange.qbk

@@ -10,7 +10,11 @@
 ``
 template<class Integer>
 iterator_range< range_detail::integer_iterator<Integer> >
-irange(Integer first, Integer  last);
+irange(Integer last);
+
+template<class Integer>
+iterator_range< range_detail::integer_iterator<Integer> >
+irange(Integer first, Integer last);
 
 template<class Integer, class StepSize>
 iterator_range< range_detail::integer_iterator_with_step<Integer, StepSize> >
@@ -37,4 +41,3 @@ Defined in the header file `boost/range/irange.hpp`
 Constant. Since this function generates a new range the most significant performance cost is incurred through the iteration of the generated range.
 
 [endsect]
-

include/boost/range/irange.hpp

@@ -217,7 +217,7 @@ namespace boost
     {
         BOOST_ASSERT( step_size != 0 );
         BOOST_ASSERT( (step_size > 0) ? (last >= first) : (last <= first) );
-        
+
         typedef typename range_detail::integer_iterator_with_step<Integer> iterator_t;
 
         const std::ptrdiff_t sz = static_cast<std::ptrdiff_t>(step_size >= 0 ? step_size : -step_size);
@@ -225,12 +225,19 @@ namespace boost
         const Integer f = step_size >= 0 ? first : last;
         const std::ptrdiff_t num_steps = (l - f) / sz + ((l - f) % sz ? 1 : 0);
         BOOST_ASSERT(num_steps >= 0);
-       
+
         return strided_integer_range<Integer>(
             iterator_t(first, 0, step_size),
             iterator_t(first, num_steps, step_size));
     }
 
+    template<typename Integer>
+    integer_range<Integer>
+    irange(Integer last)
+    {
+        return integer_range<Integer>(static_cast<Integer>(0), last);
+    }
+
 } // namespace boost
 
 #endif // include guard

test/irange.cpp

@@ -18,6 +18,23 @@
 
 namespace boost
 {
+    // Test an integer range with a step size of 1.
+    template<typename Integer>
+    void test_irange_impl(Integer last)
+    {
+        std::vector<Integer> reference;
+        for (Integer i = static_cast<Integer>(0); i < last; ++i)
+        {
+            reference.push_back(i);
+        }
+
+        std::vector<Integer> test;
+        boost::push_back(test, boost::irange(last));
+
+        BOOST_CHECK_EQUAL_COLLECTIONS( test.begin(), test.end(),
+                                       reference.begin(), reference.end() );
+    }
+
     // Test an integer range with a step size of 1.
     template<typename Integer>
     void test_irange_impl(Integer first, Integer last)
@@ -34,36 +51,52 @@ namespace boost
         BOOST_CHECK_EQUAL_COLLECTIONS( test.begin(), test.end(),
                                        reference.begin(), reference.end() );
     }
-    
+
     // Test an integer range with a runtime specified step size.
     template<typename Integer, typename IntegerInput>
     void test_irange_impl(IntegerInput first, IntegerInput last, int step)
     {
         BOOST_ASSERT( step != 0 );
-        
+
         // Skip tests that have negative values if the type is
         // unsigned
         if ((static_cast<IntegerInput>(static_cast<Integer>(first)) != first)
         ||  (static_cast<IntegerInput>(static_cast<Integer>(last)) != last))
             return;
-        
+
         std::vector<Integer> reference;
 
         const std::ptrdiff_t first_p = static_cast<std::ptrdiff_t>(first);
         const std::ptrdiff_t last_p = static_cast<std::ptrdiff_t>(last);
         const std::ptrdiff_t step_p = static_cast<std::ptrdiff_t>(step);
-        for (std::ptrdiff_t current_value = first_p; 
+        for (std::ptrdiff_t current_value = first_p;
              step_p >= 0 ? current_value < last_p : current_value > last_p;
              current_value += step_p)
             reference.push_back(current_value);
 
         std::vector<Integer> test;
         boost::push_back(test, boost::irange(first, last, step));
-        
+
         BOOST_CHECK_EQUAL_COLLECTIONS( test.begin(), test.end(),
                                        reference.begin(), reference.end() );
     }
 
+    // Test driver function that for an integer range [first, last)
+    // drives the test implementation through various integer
+    // types.
+    void test_irange(int last)
+    {
+        test_irange_impl<signed char>(last);
+        test_irange_impl<unsigned char>(last);
+        test_irange_impl<signed short>(last);
+        test_irange_impl<unsigned short>(last);
+        test_irange_impl<signed int>(last);
+        test_irange_impl<unsigned int>(last);
+        test_irange_impl<signed long>(last);
+        test_irange_impl<unsigned long>(last);
+    }
+
+
     // Test driver function that for an integer range [first, last)
     // drives the test implementation through various integer
     // types.
@@ -102,6 +135,11 @@ namespace boost
     // number of implementation branches.
     void irange_unit_test()
     {
+        // Test the single-step version of irange(last)
+        test_irange(0);
+        test_irange(1);
+        test_irange(10);
+
         // Test the single-step version of irange(first, last)
         test_irange(0, 0);
         test_irange(0, 1);
@@ -124,14 +162,14 @@ namespace boost
         test_irange(9, -9, -2);
         test_irange(10, 20, 5);
         test_irange(20, 10, -5);
-        
+
         test_irange(0, 0, 3);
         test_irange(0, 1, 3);
         test_irange(0, 2, 3);
         test_irange(0, 3, 3);
         test_irange(0, 4, 3);
         test_irange(0, 10, 3);
-        
+
         test_irange(0, 0, -3);
         test_irange(0, -1, -3);
         test_irange(0, -2, -3);