C++Talk.NET

Matthias Hofmann · Guest

Hello everybody!

When I first learned learned C++, I often encountered statements like

for ( ;; ) {}

instead of

while ( true ) {}

Also, I found code in the VC++ implementation of STL algorithms that omitted
the for-init-statement in for statements, for example in:

template <class _FwdIt, class _Ty> inline
void fill( _FwdIt _First, _FwdIt _Last, const _Ty& _Val )
{
for( ; _First != _Last; ++_First )
_First = _Val;
}

This seems to make perfect sense, but 6.5.3/1 of the C++ Standard says that
the for-init-statement cannot be omitted. Does that mean that the
implementation of fill() above is not portable? Would it have to be
rewritten as follows to be standard compliant?

template <class _FwdIt, class _Ty> inline
void fill( _FwdIt _First, _FwdIt _Last, const _Ty& _Val )
{
while ( _First != _Last )
{
_First = _Val;
++_First;
}
}

By the way, I noticed that my version of the C++ Standard defines the for
statement as follows:

for ( for-init-statement condition opt ; expression opt ) statement

I guess there is a semicolon missing right before "condition"?

--
Matthias Hofmann
Anvil-Soft, CEO
http://www.anvil-soft.com - The Creators of Toilet Tycoon
http://www.anvil-soft.de - Die Macher des Klomanagers

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James Dennett · Guest

Jiang wrote: