You begin an ITC session by starting XGAP. On most systems this is done by completing the provided line
on the command line. Ask your system administrator if this does not work. This command will create a new window, the so called GAP Window, in which GAP is awaiting your input.
During a typical ITC session various windows will be opened to display the involved tables and further information. The size of the characters displayed in these windows and hence the sizes of the windows themselves are determined by the so-called fonts used.
The XGAP package knows five different fonts,
huge (see the XGAP manual for details), but
the ITC routines use only two of them, namely
So, if the default ITC window sizes are inconvenient for you, you
need only to change the values of these two fonts. You may do this by
starting XGAP with one or two additional arguments of the form
" or "
" where font has to be a
font which is known to your system. You can get a list of all available
fonts via the command
user@host:~> xgap -small 6x12 -normal 8x13
In particular, you should use this option to change the fonts if the default fonts of XGAP do not work properly in your local installation (this may happen in some rare cases where there are too few or too many fonts).
At the top of the GAP Window opened by XGAP you will see a
``title bar'' with three buttons:
either of these will pop up a menu, in which you may choose between
You can always interrupt a computation by making the GAP Window
active and pressing CTRL-C. You will get the same effect selecting
Interrupt in the
In the GAP Window, as usual, the GAP prompt
will indicate that GAP is awaiting your input.
If it is not loaded automatically, first load the ITC package by
gap> RequirePackage( "itc" );
See RequirePackage in the GAP Reference Manual.
Then you may input a finitely presented group, say g, and a subgroup, say h, of it, the cosets of which you want to enumerate using ITC. The format of this input is the same as usual in GAP, see Chapter Finitely Presented Groups of the GAP reference manual for the details.
ITC will in several of its windows have to display generators of the free group which is used to describe the presentation. Note that ITC will use the names of the generators of this free group, if these names consist of at most three symbols. Otherwise ITC will use names of the form g1, g2, ... up to at most g99 for the generators of the free group (if the group has more than 99 generators, an error message will be given). A choice of short and easily distinguishable names for the generators of the free group is hence advisable.
Now you are ready to start the ITC using the command
Called with a group g and a subgroup h, this will open the ``Coset Table Window'', which really serves a multiple purpose:
The initial table size for the ITC Coset Table is set by default to
1000. You can change this default table size using the menu entry
change default table size in the menu of the top button
(see change default table size). If during a run of a CE the table
size does not suffice, you can extend it using the menu entry
table size (see extend table size) in the same menu.
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