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Quick Q: With arrays, why is it the case that a[5] == 5[a]?

By Adrien Hamelin | Jun 4, 2019 11:01 AM | Tags: intermediate

Quick A: See below

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

The C standard defines the [] operator as follows:

a[b] == *(a + b)

Therefore a[5] will evaluate to:

*(a + 5)

and 5[a] will evaluate to:

*(5 + a)

a is a pointer to the first element of the array. a[5] is the value that's 5 elements further from a, which is the same as *(a + 5), and from elementary school math we know those are equal (addition is commutative).

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casenet said on Jun 14, 2019 03:11 AM:



The C standard defines the [] operator as follows:

a[b] == *(a + b)

Therefore a[5] will evaluate to:

*(a + 5)

and 5[a] will evaluate to:

*(5 + a)

a is a pointer to the first element of the array. a[5] is the value that's 5 elements further from a, which is the same as *(a + 5), and from elementary school math we know those are equal (addition is commutative).[url="https://wp.me/aZ4zD" rel="dofollow"]Casenet[/url]