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5.3 Structural Manipulations • 177> list1 := sort(list1);list1 := [“a”, “b”, “c”, “d”]> list2 := sort(list2);list2 := [1, 2, 3, 5, 9]Finally, stack the two lists together.> sorted_list := [ op(list1), op(list2) ];sorted _list := [“a”, “b”, “c”, “d”, 1, 2, 3, 5, 9]The sort command can also sort algebraic expressions. See section5.1.This section, pages 172–173, gives more information about the commandsin this example.The Parts of an ExpressionTo manipulate the details of an expression, you must select the individualparts. Three easy cases for doing this involve equations, ranges, andfractions. The lhs command selects the left-hand side of an equation.> eq := a^2 + b^ 2 = c^2;eq := a 2 + b 2 = c 2> lhs( eq );a 2 + b 2The rhs command similarly selects the right-hand side.> rhs( eq );c 2The lhs and rhs commands also work on ranges.> lhs( 2..5 );