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Difference between revisions of "Extracting a Sublist"

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(it corresponds to lots of things in lots of languages. Is python special? Also, 'newly allocated' doesn't matter in this non-destructive language.)
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Please note that all list functions are indexed by 1.  
 
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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.
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Note: The sublist function corrresponds to using the slice operator in Python.  
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[[Category:CookBook]][[Category:ListRecipes]]
 
[[Category:CookBook]][[Category:ListRecipes]]

Revision as of 13:46, 24 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]

Please note that all list functions are indexed by 1.