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From this post in SO, it is clear that C supports negative indices.
Why support such a potential memory violation in a program?
Shouldn't the compiler throw a Negative Index warning at least? (am using GCC)
Or is this calculation done in runtime?
EDIT 1: Can anybody hint at its uses?
EDIT 2: for 3.) Using counters of loops in
[]of arrays/pointers indicates Run-time Calculation of Indices.
508
It is invalid. By the C standard, it explicitly has undefined behavior.
Python programming language supports negative indexing of arrays, something which is not available in arrays in most other programming languages. This means that the index value of -1 gives the last element, and -2 gives the second last element of an array. The negative indexing starts from where the array ends.
No, you cannot use a negative integer as size, the size of an array represents the number of elements in it, –ve number of elements in an array makes no sense.
Negative “From the End” Indexing in Python This means the last value of a sequence has an index of -1, the second last -2, and so on. You can use negative indexing as your advantage when you want to pick values from the end (right side) of an iterable.
The calculation is done at runtime.
Negative indices don't necessarily have to cause a violation, and have their uses.
For example, let's say you have a pointer that is currently pointing to the 10th element in an array. Now, if you need to access the 8th element without changing the pointer, you can do that easily by using a negative index of -2.
char data[] = "01234567890123456789";
char* ptr = &data[9];
char c = ptr[-2]; // 7
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