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3.4.1. 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 ::= Q[t,x,y,z];
L := [34x+y^2,'a string',[],[TRUE,FALSE]]; -- a list
L[1];  -- the list's 1st component
y^2 + 34x
-------------------------------
L[2];  
a string
-------------------------------
L[3];
[ ]
-------------------------------
L[4];  -- The 4th component is a list, itself;
[TRUE, FALSE]
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L[4][1]; -- its 1st component;
TRUE
-------------------------------
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').  
-------------------------------
L := [x^2-y,ty^2-z^3];
I := Ideal(L);
I;
Ideal(x^2 - y, ty^2 - z^3)
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