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4.4.1 Introduction to Lists
A CoCoA list is a sequence of CoCoA objects between brackets. In particular, a list may contain other lists. The empty list is []. If L is a list and N is an integer, then L[N] is the N-th component of L. If L contains sublists, then L[N_1, N_2,...,N_s] is shorthand for L[N_1][N_2]...[N_s] (see the example below). Lists are often used to build structured objects of type MAT, VECTOR, IDEAL, and MODULE.

Example 
  Use R ::= QQ[t,x,y,z];
  L := [34x+y^2,"a string", [], [TRUE, FALSE]]; -- a list
  L[1];  -- the list's 1st component
y^2 + 34x
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  L[2];
a string
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  L[3];
[ ]
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  L[4];  -- The 4th component is a list, itself;
[TRUE, FALSE]
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  L[4][1]; -- its 1st component;
TRUE
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  L[4,1];  -- the same.
TRUE
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  [1,"a"]+[2,"b"];  -- Note: one may add lists if their components are
[3, "ab"]         -- compatible (see "Algebraic Operators").
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  L := [x^2-y,ty^2-z^3];
  I := Ideal(L);
  I;
Ideal(x^2 - y, ty^2 - z^3)
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