This is documentation for Mathematica 3, which was
based on an earlier version of the Wolfram Language.
View current documentation (Version 11.2)
 Documentation / Mathematica / The Mathematica Book / Practical Introduction / Lists  /

1.8.8 Advanced Topic: Lists as Sets

Mathematica usually keeps the elements of a list in exactly the order you originally entered them. If you want to treat a Mathematica list like a mathematical set, however, you may want to ignore the order of elements in the list.


Set theoretical functions.

  • Union gives the elements that occur in any of the lists.
  • In[1]:= Union[{c, a, b}, {d, a, c}, {a, e}]

    Out[1]=

  • Intersection gives only elements that occur in all the lists.
  • In[2]:= Intersection[{a, c, b}, {b, a, d, a}]

    Out[2]=

  • Complement gives elements that occur in the first list, but not in any of the others.
  • In[3]:= Complement[{a, b, c, d}, {a, d}]

    Out[3]=