Extracting a Sublist

From Erlang Community

(Difference between revisions)
Revision as of 15:02, 14 July 2007 (edit)
Alexaandru (Talk | contribs)
m (It's the lists itselves that are indexed by 1, not the "list functions".)
← Previous diff		 Current revision (23:47, 11 September 2007) (edit) (undo)
Serpent (Talk | contribs)
(Correct the description of sublist/3)
 
Line 1: Line 1:
== Problem == == Problem ==
-Given a list, extract a segment specified by a start and an end index (inclusive). +Given a list, extract a segment specified by a start index and an optional length.
== Solution == == 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. +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 point in the list and the maximum number of elements to extract.
<code> <code>

Current revision

[edit] Problem

Given a list, extract a segment specified by a start index and an optional length.

[edit] 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 point in the list and the maximum number of elements to extract. 

% 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]

Please note that all functions assume the position numbering starts at 1.

Retrieved from "http://www.trapexit.org/Extracting_a_Sublist"
Erlang/OTP Projects
Personal tools