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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 ------------------------------- 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 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) ------------------------------- ```