[with patch, positive review] conversion of Permutations to GAP not implemented

[mhansen]

The following fails

sage: p = gap(Permutation('(1,2,3)'))
sage: q = gap(Permutation([()]))
sage: gap.Group([p, q])

because

sage: gap(Permutation((1,2,3)))
[ 2 3 1 ]

[wdj]

I don't see how this fixes the original problem. I get this:

sage: p = gap(Permutation('(1,2,3)'))                                                                                              
sage: q = gap(Permutation('()'))                                                                                       
---------------------------------------------------------------------------                                            
ValueError                                Traceback (most recent call last)
<snip>


ValueError: invalid literal for int() with base 10: ''

and this:

sage: q = gap(Permutation(()))
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<snip>

TypeError: not enough arguments for format string

It seems to me you want Permutation to work like PermutationGroupElement? does here:

sage: p = gap(PermutationGroupElement('(1,2,3)'))
sage: q = gap(PermutationGroupElement('()'))
sage: gap.Group([p, q])
Group( [ (1,2,3), () ] )
sage: gap.Group([p]) == gap.Group([p, q])
True

Is that correct?

[mhansen]

Actually, the original issue was this:

sage: p = gap(Permutation('(1,2,3)'))
sage: q = gap(Permutation([()]))
sage: gap.Group([p, q])
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)

Those things that you encountered are "bugs" in the constructor of Permutation. I always construct Permutations from their list notation.

[saliola]

This patch should get a positive review because it fixes the conversion to gap problem:

sage: p = Permutation('(1,2,3)')
sage: q = Permutation([()])
sage: gap.Group([p,q])
Group( [ (1,2,3), () ] )

The other issues noticed by wdj are problems with the Permutations constructor function, and I will open a new ticket for them.

[saliola]

The new ticket is here: #4569

[mabshoff]

Merged in Sage 3.2.1.alpha0