I have the following code:
a=b=vector(ring, 2)
a = ([r1,r2])
b =a
a[0] = s1
Then b[0] changes too but I want b[0] be r1. And I do not want to do something like this:
b = ([a[0],a[1]])
which works but inconvenient because of possible high dimensions of vectors.
Attention, pitfall:
a = b = vector(QQ,2)
is NOT a shortform of
a = vector(QQ,2)
b = vector(QQ,2)
The first creates exactly one vector object, a an b refer to the same object. The second creates two independent objects, a and b refer to different objects.
print a == b, a is b
shows the difference.
Use this:
b = a[:]
to copy the vector into an independent vector.
Asked: 2017-01-16 00:43:12 +0200
Seen: 284 times
Last updated: Jan 17 '17
Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.