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2.5.1 Introduction to LIST
A CoCoA list is a sequence of CoCoA objects between square brackets. See also List Constructors. The objects may be of different types, though a well-designed algorithm will likely create lists of objects of a single type.

In particular, a list may contain other lists. The empty list is [] . We use square brackets to index into a list. If L is a non-empty list and N is an integer (between 1 and len(L) ), then L[N] is the N -th component of L ; indexes start from 1.

If L contains sublists, we can write L[N_1, N_2,...,N_s] as shorthand for L[N_1][N_2]...[N_s] (see the example below).

Lists are often used to build structured objects of type MAT , MODULEELEM , IDEAL , and MODULE .

Example
/**/  use R ::= QQ[t,x,y,z];
/**/  L := [34*x+y^2, "a string", [], [True, False]]; -- a list
/**/  L[1];  -- the 1st component
y^2 +34*x
/**/  L[2];
a string
/**/  L[3];
[ ]
/**/  L[4];  -- The 4th component is a list, itself;
[true, false]
/**/  L[4][1]; -- its 1st component;
true
/**/  L[4,1];  -- the same.
true

/**/  [1,"a"]+[2,"b"];  -- NOTE: one may add lists if their components
[3, "ab"]               -- are compatible (see "Algebraic Operators").

/**/  L := [x^2-y, t*y^2-z^3];
/**/  I := ideal(L);
/**/  I;
ideal(x^2 -y, t*y^2 -z^3)