How to remove duplicates from a matrix without using unique?

d = [1 6 -1 5 6 7 0 5 6 0 8 0]

a = [-1 0 1 5 6 7 8]

How can I convert the vector d to vector a?

Please dont use unique

Answer 1

[Walter Roberson]

[~, a]=findgroups(d);

Answer 2

[John D'Errico]

How could you use the output of a sort to help? Why not make an effort?