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Operator precedence C++

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Operator precedence C++

amitdhar	4 Feb, 2008 - 01:19 PM Post #1
New D.I.C Head Joined: 1 Feb, 2008 Posts: 33 Thanked: 1 times My Contributions	int a=10,c; c= a++ + ++a + a-- - --a; cout<<c; The above code is giving output 20. What is the sequence of operations in the above expression? Becasue according to operator precedence post increment/decrement has got higher precedence than pre increment/decrement.
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William_Wilson	RE: Operator Precedence C++ 4 Feb, 2008 - 01:24 PM Post #2
lost in compilation Joined: 23 Dec, 2005 Posts: 4,101 Thanked: 25 times Dream Kudos: 3275 Expert In: Java, C, Javascript My Contributions	i won't give you the answer exactly as wanted, but i will help you out with an example: CODE if a=0; cout<<a; //is 0 cout<<a++; //is stil 0, as a post increment the value of a is used first //now a is 1 cout<<++a;// the pre increment will result in the addition before the cout, thus 2 is displayed The only trick to your above example is that all operations take place on a single line, just do all pre order elements, and since nothing other than assignment is applied to them after a post operations, you can effectively remove them from the equation.
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Bench	RE: Operator Precedence C++ 4 Feb, 2008 - 03:38 PM Post #3
D.I.C Addict Joined: 20 Aug, 2007 Posts: 683 Thanked: 24 times Dream Kudos: 150 Expert In: C/C++ My Contributions	QUOTE(amitdhar @ 4 Feb, 2008 - 09:19 PM) int a=10,c; c= a++ + ++a + a-- - --a; cout<<c; The above code is giving output 20. What is the sequence of operations in the above expression? Becasue according to operator precedence post increment/decrement has got higher precedence than pre increment/decrement. Whatever you think the operator precedence might be is irrelevant. There's no correct answer, its undefined behaviour according to the language standard. http://www.research.att.com/~bs/bs_faq2.ht...valuation-order http://www.c-faq.com/expr/ieqiplusplus.html
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KYA	RE: Operator Precedence C++ 4 Feb, 2008 - 04:33 PM Post #4
#include <nerd.h> Joined: 14 Sep, 2007 Posts: 5,850 Thanked: 159 times Dream Kudos: 1375 My Contributions	I find it more helpful to have a goal when solving a problem like this. What is the point of the code segment? --KYA
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Bench	RE: Operator Precedence C++ 5 Feb, 2008 - 02:33 AM Post #5
D.I.C Addict Joined: 20 Aug, 2007 Posts: 683 Thanked: 24 times Dream Kudos: 150 Expert In: C/C++ My Contributions	QUOTE(KYA @ 5 Feb, 2008 - 12:33 AM) I find it more helpful to have a goal when solving a problem like this. What is the point of the code segment? Usually, I believe such expressions are used as an experiment of evaluation order. Unfortunately, it doesn't work for anything beyond compiler-specific behaviour, because compilers are free to evaluate each component in any order which they see fit, hence why the OP may not have gotten the output which they were expecting
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amitdhar	RE: Operator Precedence C++ 5 Feb, 2008 - 06:36 AM Post #6
New D.I.C Head Joined: 1 Feb, 2008 Posts: 33 Thanked: 1 times My Contributions	QUOTE(William_Wilson @ 4 Feb, 2008 - 02:24 PM) i won't give you the answer exactly as wanted, but i will help you out with an example: CODE if a=0; cout<<a; //is 0 cout<<a++; //is stil 0, as a post increment the value of a is used first //now a is 1 cout<<++a;// the pre increment will result in the addition before the cout, thus 2 is displayed The only trick to your above example is that all operations take place on a single line, just do all pre order elements, and since nothing other than assignment is applied to them after a post operations, you can effectively remove them from the equation. That is not clear to me.. even after all the pre order elements executed and post one ignored.. the given output of 20 is not coming.
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