Ellipsis range notation

[robertwb]

There have been proposal to add syntax to SAGE similar to magma/mathmatica/etc 1..n for ranges. See the mailing list for much discusssion.

Component: user interface

Issue created by migration from https://trac.sagemath.org/ticket/702

[robertwb]

Attachment: ellipsis_iterator.diff.gz

Attachment: ellipsis_iterator2.diff.gz

[robertwb]

comment:1

The above patches are one such proposal. NOTE: it has not been decided whether or not to include this feature. However, I like it.

sage: [1..10]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
sage: n = 5
sage: [1..n]
[1, 2, 3, 4, 5]
sage: [0,2,..,10]
[0, 2, 4, 6, 8, 10]
sage: [0,2,..,10,20..30]
[0, 2, 4, 6, 8, 10, 20, 22, 24, 26, 28, 30]

sage: (0,2,..,10)       
<generator object at 0xc57cd78>
sage: A = (5,7,..)
sage: [A.next() for _ in range(20)]
[5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25]

And a non-trivial example

sage: L = [1..5]
sage: [L[4], .., next_prime(10), 3, 2, 1]
[5, 6, 7, 8, 9, 10, 11, 3, 2, 1]

[robertwb]

Attachment: ellipsis_iterator3.diff.gz

[robertwb]

comment:2

Fixed:

sage: A = (5,7,..)
sage: [A.next() for _ in range(10)]
[5, 7, 9, 11, 13, 15, 17, 19, 21, 23]

[robertwb]

Attachment: ellipsis_iterator4.diff.gz

[robertwb]

comment:3

Fixed an issue with double quotes, and now this works as well

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

[williamstein]

comment:4

Attachment: ellipsis_iterator1-4.hg.gz

Applied. (And I fixed a few bugs.)

[robertwb]

comment:5

[1,2,..,-10] should return the empty list.

[robertwb]

Attachment: ellipsis-empty-range.hg.gz

[robertwb]

comment:6

Fixed.

sage: [1,2..-1]
[]
sage: [10..1]
[]
sage: [1..10]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
sage: [1..10,step=2] # no extra preparsing needed
[1, 3, 5, 7, 9]

[jasongrout]

comment:7

Why doesn't [10..1] return [10,9,8,7,6,5,4,3,2,1]?

[williamstein]

comment:8

I don't think this should be an error:

sage: [1..5, step=0.5]
<type 'exceptions.TypeError'>: unable to coerce element to an integer

i.e., the universe stuff should take into account the step if given.

[williamstein]

comment:9

Fixed now by Robert...