[GAP Forum] Urgent Issue on GAP...

[Sergei Haller]

On Tue, 8 Mar 2005, Justin Walker (JW) wrote:

JW> On Mar 8, 2005, at 8:13, Dan Rossul wrote:
JW> 
JW> > When I try the command:
JW> > 
JW> > gap> g:=Group((1)(2)(3,4));
JW> > Syntax error: ) expected
JW> 
JW> On input, "(1)(2)..." is invalid.  The parser expects a '*' to be used;
JW> juxtaposition does not mean "group operation".

well, it does for permutations, so (3,4)(5,6) or (3,4)(2) are perfectly 
valid.

The thing is that GAP seems to interpret the command line from left to 
right and decides that the first object in (1)(2)(3,4) is an integer, the 
second object is (2), an integer, too, but juxtaposition of integers in 
parentheses is not accepted.

if you use * then (1)*(3,4) is fine, since right hand side is a 
permutation, the left hand side (1) is interpreted as the identity 
permutation in parentheses. So 1*(3,4) works as well.

Here, (2)*(3,4) does not work, since (2) is interpreted as an integer and 
(3,4) as a permutation.

Back to the original question: 

As Dan pointed out, the input like Group((3,4)) does work.
Why would you like to use Group((1)(2)(3,4))?

is the permutation (1)(2)(3,4) generated by some function?
If yes, you might consider using something like PermList([1,2,4,3]);
as I wrote in my last post.


Best regards,

        Sergei
-- 
--------------------------------------------------------------------  -?)
         eMail:       Sergei.Haller at math.uni-giessen.de               /\\
-------------------------------------------------------------------- _\_V
Be careful of reading health books, you might die of a misprint.
                -- Mark Twain