Expected Behavior

Write a function ngram(arglist, startpos, length) that returns the n-gram from arglist of length length starting at position startpos, if one exists; and [] otherwise. (The very first element of the list is at position 0. Negative positions refer to counting backwards from the end of the list.)

Examples

Call: ngram([11,22,33,44,55], 0, 3) Return value: [11,22,33]

Call: ngram([11,22,33,44,55], 2, 3) Return value: [33,44,55]

Call: ngram([11,22,33,44,55], 3, 3) Return value: []

Call: ngram([11,22,33,44,55], -4, 3) Return value: [22,33,44]