clist_slice

Slice a list, i.e. extract a sequence of items from the beginning and/or ending positionsand/or matching items.

%let res=%clist_slice(clist, beg=, ibeg=, end=, iend=, mark=%str(%"), sep=%quote(,));

Arguments

• clist : a list of formatted (e.g., comma-separated quote-enhanced) strings;
• beg : (option) item to look for in the input list; the slicing will 'begin' from the first occurrence of beg (with quotes); if not found, an empty list is returned;
• end : (option) ibid, the slicing will 'end' at the first occurrence of end; if not found, the slicing is done till the last item;
• ibeg : (option) position of the first item to look for in the input list; must be a numeric value >0; if the value is > length of the input list, an empty list is returned; incompatible with beg option (see above); if neither beg nor ibeg is passed, ibeg is set to 1;
• iend : (option) ibid, position of the last item; must be a numeric value >0; in the case iend<iend, an empty list is returned; in the case, iend=ibeg then the item beg (in position ibeg) is returned; incompatible with end option (see above); if neither end nor iend is passed, iend is set to the length of list;
• mark, sep : (option) characters/strings used respectively as a "quote" and a separator in the input list; default: mark=str(%"), and" sep=%quote(,), i.e. the input clist is a comma-separated list of quote-enhanced items; see %clist_unquote for further details.

Returns

res : output list defined as the sequence of items extract from the input list list from the ibeg-th position or the first occurrence of beg, till the iend-th position or the first occurrence of end (after the ibeg-th position).

Examples

%let clist=("a","bb","ccc","dddd","bb","fffff");
%let res=%clist_slice(&clist, beg=bb, iend=4);

returns: res=("bb","ccc"), while

%let res=%clist_slice(&list, beg=ccc);
%let res2=%clist_slice(&list, ibeg=bb, end=bb);
%let res3=%clist_slice(&list, beg=ccc, iend=3);

return respectively: res=("bb","ccc","dddd","bb","fffff"), res2=("bb","ccc","dddd") and res3=("ccc").

Run macro %_example_clist_slice for more examples.

Notes

1. The parameters beg and end shall be passed without the quotes ".
2. The first occurrence of end is necessarily searched for in list after the ibeg-th position (or first occurrence of beg).
3. The item at position iend (or first occurrence of end) is not inserted in the output res list.
4. The macro returns an empty list res= instead of () when there is no match.
5. The macro will not return exactly what you want if the symbol $ appears somewhere in the list. If you need to use $, you can reset the global macro variable G_PING_UNLIKELY_CHAR (see _setup_ file) to another dumb (unlikely) character of your own.

See also

%list_slice, %clist_compare, %clist_append, %clist_unquote.