-----Original Message----- From: Christian Böhme <monodhs@xxxxxx> To: gcc-help@xxxxxxxxxxx Date: Fri, 15 Jun 2007 22:09:10 +0200 Subject: Re: increasing var twice in a statement Chris Wolstenholme wrote: > 1) The statement was a = ++b + ++b; > 2) b=3 before this statement > 3) The operator ++ on the right hand side of the + operator is executed > first by rules of precedence. As it is pre-increment, b becomes 4. .... yielding a (hypothetical) temporary holding the value 4 as the right hand operand of "+". > 4)The operator ++ on the left hand side of the + operator is then > executed. As it is also pre-increment, b is again altered to become 5. .... yielding a(nother hypothetical) temporary holding the value 5 as the left hand operand of "+". > 5) Then the operator + is executing adding b (now 5) to b (still 5). .... which would yield 9 (= 5 + 4) according to the above. > That's only two increments of b, but both before the addition operator. Try to derive a syntax tree from the expression and evaluate it by walking that tree using your defined order and you'll arrive at a = 9. ______________________________-- The question was about what result a C standard would dictate, but the C standard in effect says no result can be relied upon in this kind of situation. Tim Prince
