I have a question about the nature of the final argument to
the count and count_if algorithms.  Must this argument
support post-increment, operator +=, operator + and assigment,
or something else?

More precisely, the public-domain HP implementation of count()
is:
  template < class InputIterator, class T, class Size >
  void count( InputIterator first, InputIterator last,
              const T &value, Size &n ) {
    while ( first != last )
      if ( *first++ == value ) n++;
  }

Why couldn't the interesting expression be any of:
  n += 1
  n -= -1
  n = n + 1
  etc?

The WP doesn't seem to provide sufficient guidance (or else
I couldn't find it).

Bill Law


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