list_index

Extract elements from a list at given position(s).

%let res=%list_index(list, index, sep=%quote( ));

Arguments

• list : a list of (e.g., blank separated) items;
• index : a list of numeric indexes providing with the positions of items to extract from list; must that the values of items in index should be < length of the list and >0;
• sep : (option) character/string separator in input list list (but not index); default: %quote( ), i.e. sep is blank.

Returns

res : output list defined as the sequence of elements extract from the input list list so that:

• the i-th element in res is equal to the j-th element of list where the position j is given by the i-th element of index.

Examples

%let index = 3 5 2 100 4 1;
%let list=a bb ccc dddd bb fffff;
%let res=%list_index(&list, &index);

returns: res=ccc bb bb dddd a since the index 100 is ignored.

Run macro %_example_list_index for more examples.

Notes

1. Indexes larger than the length of the input list list are ignored, while whenever one index is <0, and error is generated.
2. For wrongly typed indexes (e.g. non numeric index), an error is also generated.
3. In general case of error, the output res returned is empty (i.e. res=).

See also

%clist_index, %list_slice, %list_compare, %list_count, %list_remove, %list_append, INDEX.