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From: David Brown <david.brown@hesbynett.no>
Newsgroups: comp.lang.c,comp.lang.c++
Subject: Re: Can you please verify that the analysis of these C functions is
 correct?
Date: Sun, 23 Jun 2024 14:38:06 +0200
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On 23/06/2024 08:52, Bonita Montero wrote:
> Am 22.06.2024 um 20:50 schrieb Richard Damon:
> 
>> Prior to that, it was allowed to compute the order of the terms being 
>> output in any order, as the call to operator <<(ostream& strm, T& 
>> value) was allowd to compute value before resolving stream (as the 
>> value from the previous operator <<, which caught enough people off 
>> guard.
> 
> With a left-associative operator the result of the left part has to be
> calculated before it can be used with the right part.

Both the left part and the right part need to be evaluated before the 
operator between them can be evaluated - but the two parts can be 
evaluated in either order (or even interleaved in their evaluation). 
Associativity is irrelevant.


Before C++17 (which added the rules for sequencing for shifts, and made 
a few other changes), if you had:

	foo() << bar()

then the compiler could evaluate bar() then foo(), or foo() then bar(). 
It can still happily arrange them as it wants for "foo() + bar()".

<https://en.cppreference.com/w/cpp/language/eval_order>