Returns the nth element of a list.
與 .wl 參考的差異： A failed nested `Part` rebuilds the whole chain
Part extraction using `[[]]` notation
The `[[n]]` notation is equivalent to `Part[..., n]`.
Part extraction from variables
Out of bounds error
Attempting to access an index beyond the list length returns an error.
Part[{7, 6, 4}, 2]
→ 6{1, 2, 3}[[2]]
→ 2{a, b, c, d}[[3]]
→ cx = {10, 20, 30}; x[[2]]
→ 20list = {a, b, c}; list[[1]]
→ a{1, 2, 3}[[5]]
→
Part::partw: Part 5 of {1, 2, 3} does not exist.
{1, 2, 3}[[5]]x = {1, 2}; x[[10]]
→
Part::partw: Part 10 of {1, 2} does not exist.
{1, 2}[[10]]