Hi,
I have a question regarding the ptr_fun function adaptor.  I am rather new to the STL
so please be patient with me.

The following sample code produces an error with both STL-Port 3.0 (an port of
the SGI implementation) and the Microsoft STL, using VC++ 5.0:

struct MyStruct { int a; };

bool MyPred(const MyStruct& x)
{
    return x.a != 0;
}

void fn()
{
    not1(ptr_fun(MyPred));
}

Compiling with the Microsoft STL, I get the following error:

functional(120) : warning C4181: qualifier applied to reference type ignored
functional(120) : error C2529: '_X' : reference to reference is illegal

functional(120)  is in the body of unary_negate:
  // TEMPLATE CLASS unary_negate
template<class _Ufn>
 class unary_negate
 : public unary_function<_Ufn::argument_type, bool> {
public:
 explicit unary_negate(const _Ufn& _X)
  : _Fn(_X) {}
>>>>> bool operator()(const _Ufn::argument_type& _X) const     <<<<<
  {return (!_Fn(_X)); }
protected:
 _Ufn _Fn;
 };

The STL-Port delivers similar errors:
stl_function.h(193) : warning C4181: qualifier applied to reference type ignored
stl_function.h(193) : error C2529: 'x' : reference to reference is illegal

emplate <class Predicate>
class unary_negate :
    public unary_function<typename __UNARY_ARG(Predicate,argument_type), bool> {
protected:
    Predicate pred;
public:
    explicit unary_negate(const Predicate& x) : pred(x) {}
>>>>    bool operator()(const typename Predicate::argument_type& x) const { return !pred(x); }  <<<<
};

--
I am tempted to simply change the operator() into
     bool operator()(typename Predicate::argument_type x) const { return !pred(x); }
Works fine if I do this.

So: Did I find a bug in the STL or did I use the function adaptors incorrectly?
Also: Is it acceptible to obmit the reference & in the operator() operator?

Any comments welcome.

Greetings,
-- J   rgen



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