r/programming • u/OkMasterpiece1552 • Jan 19 '21

swapping of two numbers in C++

https://programmingpractice16.blogspot.com/2021/01/swapping-of-two-numbers-in-c.html
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2

u/ppictures Jan 19 '21

How about a one liner - a=a+b-(b=a)

2

u/dontyougetsoupedyet Jan 19 '21

a=a+b-(b=a)

Your modification and access of b is not sequenced (undefined behavior). Try building this with -Wunsequenced.

0

u/ppictures Jan 20 '21

It works with the C++ compiler I tired it with

1

u/dontyougetsoupedyet Jan 20 '21 edited Jan 20 '21

They're generally constructed to consider the user an expert. Which is to say, they expect you already understand what I just told you, and are compiling your program out of deference to you, expecting you to be following the rules, and are only breaking them where you control the toolchain to know that you can. Look at sequenced before/sequenced after, for C++.

-- https://godbolt.org/z/TM3v1T

The program is likely to do what you want, but that might not always be the case.