From: musiphil@bawi.org   
      
   On 2012-03-16 06:31, Zeljko Vrba wrote:   
   > Using << for stream output is, IMO, bad form too, and was an   
   > extremely bad idea when streams were designed.  The notation is   
   > severely misleading as it implies sequencing where there is none.  I   
   > have been bitten numerous times by something looking as innocuous as   
   > cout << a() << b() << endl; but where a and b had some side-effects.   
   > This looks like sequencing, but is in actuality a series of function   
   > calls with unspecified order of evaluation with no sequence point in   
   > between.  Bad notation indeed.   
      
   The unspecified order of evaluation is a common thing in C++ that   
   programmers should be aware of, and it is a bad practice to combine   
   side effects (order-sensitive ones, especially) with printing, anyway.   
   (It's analogous to putting a mutating operation inside an assert().)   
   So I don't think the problem lies in the notation.   
      
   > This   
   >   
   > cout , a() , b() , endl;   
   >   
   > looks possibly a bit uglier, but it would ensure proper sequencing.   
      
   I would say that's much more dangerous than overloading '<<'. '<<' was   
   a new application to streams, so introducing the overloaded '<<'   
   didn't change the meaning of existing programs. However, it's not the   
   case for ',' which has had an established meaning for all types of   
   expressions, so assigning a new meaning to it would create a big   
   confusion.   
      
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