How to concatenate 2 vectors in a third ...

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Recently there was a question about this on sage-devel, which led to the following nice suggestion:

sage: a = vector([1,2,3])
sage: b = vector([4,5])
sage: from itertools import chain
sage: c = vector(chain(a,b)); c
(1, 2, 3, 4, 5)

Alternate solution :

sage: vector(vector([1, 2, 3]).list()+vector([4, 5]).list())
(1, 2, 3, 4, 5)

Hence :

sage: def concatenate_vectors(*x):
....:     return vector(reduce(lambda a,b:a+b, map(lambda u:u.list(), x)))
....: 
sage: concatenate_vectors(vector([1, 2, 3]), vector([4, 5]), vector([6]))
(1, 2, 3, 4, 5, 6)

HTH,