Partfrom

Partfrom is a term used in sequence processing to describe an operation that returns the trailing portion of a sequence starting at a specified position. In this sense, it behaves like a suffix extraction or slice operation, returning all elements from a given index to the end of the sequence. The concept is commonly expressed in functional and imperative contexts as partfrom(sequence, index).

Formal definition and behavior: For a sequence S and a non-negative integer k, partfrom(S, k) yields the subsequence consisting of S[k], S[k+1], ..., S[n-1], where n is the length of S. If k is 0, partfrom(S, 0) returns the entire sequence. If k is equal to or greater than the length of S, the result is the empty sequence. Some implementations allow negative indices, interpreting them as counting from the end, though this varies by language.

Examples: partfrom([1, 2, 3, 4], 2) returns [3, 4]. partfrom("abcdef", 3) yields "def". In logic programming or query languages, partfrom may be expressed as a rule or function that selects the tail from a given starting point.

Relation to other operations: Partfrom is closely related to slicing, substring, and tail operations. It is often contrasted with head or drop operations, which remove a portion rather than extract the remaining part. In lazy or view-based implementations, partfrom can be efficient because it might reference the original data without copying.

Applications: It is used in data processing, text manipulation, algorithm design, and streaming workflows where processing begins at a dynamic offset. Variants may allow starting from a condition rather than a fixed index, yielding the first position that satisfies a predicate.