Is chars[4] and 4[chars] the same in C? Why?

2018-07-01 02:15:15

This question already has an answer here:

With arrays, why is it the case that a[5] == 5[a]? 17 answers

In raw C, the [] notation is just a pointer math helper. Before [] , you'd look for the fourth char in the block pointed to by ptr like:

*(ptr+4)

Then, they introduced a shortcut which looked better:

ptr[4]

Which transaltes to the earlier expression. But, if you'd write it like:

4[ptr]

This would translate to:

*(4+ptr)

Which is indeed the same thing.

Because a[b] is exactly the same as *(a+b), and + is commutatitve.

chars[4] is *(chars+4) , and 4[chars] is *(4+chars)

http://c-faq.com/aryptr/joke.html试试这个来测试编译：http://codepad.org/

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