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1.1.7 Tutorial: lists

A convenient way of "putting together" many values in CoCoA-5 is to put them into a LIST. Though the CoCoA-5 name is LIST the data-structure more closely resembles a vector in C++ than a list in C++.

CoCoA-5 does not impose restrictions on the values a LIST may contain; nevertheless it usually makes most sense if the values are all of the same type (e.g. all integers, all polynomials).

A list may be created in several ways. The simplest is to write out the entries explicitly. Another is to start with an empty list, and the append new elements in a loop. There is also a convenient syntax inspired by the mathematical notation for sets.

If you have a list, you can find out how many elements it contains using the function len. You can also iterate over the elements of a list using the foreach loop command.

Example

/**/ [2,3,5]; // list containing the elements 2,3,5 in that order [2, 3, 5] /**/ 1..5; // integer range [1, 2, 3, 4, 5] // Now create a list using "append": /**/ L := []; // start with the empty list in L /**/ for i := 1 to 5 do append(ref L, i^2); endfor; /**/ println L; [1, 4, 9, 16, 25] /**/ [ n in L | IsEven(n)]; // list containing even values [4, 16] /**/ [ n^2 | n in L and n < 10]; [1, 16, 81] /**/ len(L); 5 /**/ foreach n in L do print n," "; endforeach; 1 4 9 16 25