Generate a list of linearly spaced NUMERIC values as an arithmetic progression.

%let seq=%list_sequence(len=, start=, step=, end=, sep=%quote( ));

len : (option) lenght of the output generated list; it can be omitted if and only if all other options below (e.g., start, end and step) are present, and then it is set to floor[(end - start)/ step + 1];
start : (option) starting value of the generated list, i.e. the first element in the output list will be start; default: start=1; when omitted, it is set to:
- end - step * (len-1) when all other options are present,
- 1 otherwise;
step : (option) "step" between the items in the generated list, i.e. the difference/space between two consecutive items in the output list will be equal to step; step must be non-zero; when omitted, it is set to:
- (end-start)/(len-1) when all other options are present,
- 1 otherwise; further note that step is "forced" to 1 when start and end are passed, but len is not;
end : (option) ending value of the generated list; note that depending on the other settings (e.g., len, start and step), the last element in the output list will not necessary be equal to end; when omitted, it is set to: start + (len - 1) * step;
sep : (option) character/string separator in input list; default: %quote( ), i.e. sep is blank.

seq : output arithmetic list of evenly spaced items of lenght len and of the form start start+step start+2*step ....

The following examples:

%let seq1=%list_sequence(len=10);
%let seq2=%list_sequence(len=10, start=10);
%let seq3=%list_sequence(len=10, end=20, step=2);

return seq1=1 2 3 4 5 6 7 8 9 10, seq2=10 12 13 14 15 16 17 18 19 20, and seq3=2 4 6 8 10 12 14 16 18 20, respectively, while:

%let seq4=%list_sequence(len=10, start=10, step=-1);

%let seq5=%list_sequence(len=10, end=10, step=-1);

return seq1=10 9 8 7 6 5 4 3 2 1 and seq2=19 18 17 16 15 14 13 12 11 10. Note also that:

%let seq6=%list_sequence(start=1, end=20, step=3);

will return seq1=1 4 7 10 13 16 19, hence excluding 20 from the list.

Run macro %_example_list_sequence for examples.

When step is positive (resp. negative), the last element in the output list is the largest value start + i * step that is less (resp. greater) than or equal to end.
This macro is obviously inspired by the linspace and colon, : operators in Matlab, and xrange operator in Python.