Question

Choose the correct syntax to index each of the following elements from a list, arr.
arr(3)
arr(-2)
arr(1)
arr(4)
First element of the list
Fourth element of a list
Last element of the list
Second to last element of the list

Answer 1

I need to know which language/indexing convention you mean (0-based vs 1-based, and whether negative indices are supported). The four candidate syntaxes you gave (arr(3), arr(-2), arr(1), arr(4)) behave differently in different languages. Here are the common cases — pick the one that matches your environment.

If you mean Python-style (0-based, negative indexing allowed) — using square brackets in real code:
- First element: arr[0]
- Fourth element: arr[3]
- Last element: arr[-1]
- Second-to-last element: arr[-2]

If you mean MATLAB-style (1-based, parentheses for indexing):
- First element: arr(1)
- Fourth element: arr(4)
- Last element: arr(end) (or arr(length(arr)))
- Second-to-last element: arr(end-1) (or arr(length(arr)-1))

If you intended the four specific syntaxes you listed to be matched to the four descriptions, tell me the language (or whether indexing is 0- or 1-based) and the list length, and I’ll map them exactly.