From Erlang Community

Revision as of 22:39, 3 September 2006

Problem

Given a list, extract a segment specified by a start and an end index (inclusive).

Solution

Use the lists module sublist/2 or sublist/3 functions. The sublist/2 function takes the first N elements from a list, while the sublist/3 function takes a starting and ending point in the list.

% Take the first 5 elements of a list
1> L = [1,2,3,4,5,6,7,8,9,10].
[1,2,3,4,5,6,7,8,9,10]
2> lists:sublist(L,5).
[1,2,3,4,5]

% Take 5 elements from a list, starting from the third position.
3> lists:sublist(L,3,5).
[3,4,5,6,7]

A call to either sublist will a return a newly allocated list holding the elements of the given segment. Please note that all list functions are indexed by 1.

Note: The sublist function corrresponds to using the slice operator in Python.