secondlast

Secondlast is a term used to describe the second-to-last element in a finite sequence. It is synonymous with the penultimate element, though penultimate is more common in formal mathematical writing; secondlast appears in casual language and in programming contexts as a practical label or function name.

For a sequence x1, x2, ..., xn with n >= 2, the secondlast is x_{n-1}. In everyday language and in many programming scenarios, it is defined as the element immediately preceding the final one.

In programming, secondlast is often obtained by indexing from the end. Languages with negative indices allow direct access using -2, for example Python: a[-2], Ruby: arr[-2]. Languages without negative indexing require a length-based calculation, such as JavaScript: arr[arr.length - 2], or Java: list.get(list.size() - 2).

Examples help illustrate the concept. The list [3, 7, 2, 9] has a secondlast element equal to 2, and the string "hello" has 'l' as its secondlast character.

Ambiguities arise when the sequence contains fewer than two elements; in such cases the secondlast may be undefined or trigger an error. In practice, code and algorithms typically verify the length before attempting to access the secondlast.

See also: penultimate, last, second-to-last, antepenultimate. The term secondlast often appears as a variable name or function name in programming, reflecting its informal status relative to the established term penultimate.