[STDCXX-693] std::valarray::sum does not work correctly for udt that has nonzero default value

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 4.2.0, 4.2.1
• Fix Version/s: 4.3.0
• Component/s: 26. Numerics
• Severity: Incorrect Behavior
• Assignee: Martin Sebor
• Reporter: Travis Vitek
• Created: 10/Jan/08 22:07
• Updated: 02/Jun/08 18:44

Description

#include <cassert>
#include <valarray>

struct S
{
// this ctor should not be required
S ()
: value (21)
{
}

S (int v)
: value (v)
{
}

S (const S& rhs)
: value (rhs.value)
{
}

S& operator+= (const S& rhs)

{ value += rhs.value; return *this; }

int value;
};

int main ()
{
const std::valarray<S> b (S (10), 1); // 10 elements with value 1
assert (b.sum ().value == 10);

return 0;
}

The wording in the standard seems to imply that the returned value should be a copy of one of the elements, and that op+= should be called on all of the other elements. If this is the case, then this an additional issue that would be detectable in user code [the user can count how many times the op+= is invoked]. This issue may apply to the min() and max() methods as well.