GAP.jl Julia package

This repository contains the GAP.jl Julia package, as well as the GAP packages JuliaInterface and JuliaExperimental developed for the GAP-Julia integration as part of the OSCAR project.

WARNING: GAP.jl is intended as a low-level interface between GAP and Julia. Therefore, for the most part it does not attempt (besides some general conveniences) to provide a very “Julia-ish” interface to GAP objects and functions, nor a “GAP-ish” interface to Julia objects and functions. Instead, this is left to higher-level code, for example in the Oscar.jl package.

Install

To install this package in Julia:

using Pkg; Pkg.add("GAP")

Basic usage

After entering the following in Julia,

using GAP

one may access any global GAP variable by prefixing its name with GAP.Globals., and call GAP functions like Julia functions. For example:

julia> GAP.Globals.SymmetricGroup(3)
GAP: SymmetricGroup( [ 1 .. 3 ] )

The Julia types Int64 and Bool are automatically converted to GAP objects when passed as arguments to GAP functions. Several others basic types of objects can be converted using the GapObj constructor. For example, here we convert a Vector{Int} to a GAP list:

julia> x = GapObj([1,2,3])
GAP: [ 1, 2, 3 ]

For nested objects, one can use the optional recursive keyword argument:

julia> GapObj([1,2,[3,4,5]])
GAP: [ 1, 2, <Julia: [3, 4, 5]> ]

julia> GapObj([1,2,[3,4,5]]; recursive=true)
GAP: [ 1, 2, [ 3, 4, 5 ] ]

Converting GAP objects to native Julia objects is done using suitable Julia constructors. For example, to convert the GAP list of integers we defined earlier back to Julia, we might do this:

julia> Vector{Int}(x)
3-element Vector{Int64}:
 1
 2
 3

You can temporarily switch to a GAP prompt using GAP.prompt():

julia> GAP.prompt();
gap> G := SymmetricGroup(5);
Sym( [ 1 .. 5 ] )
gap> quit;

julia> GAP.Globals.G
GAP: Sym( [ 1 .. 5 ] )

For more information on these and other capabilities of this package, please consult the GAP.jl manual.

Contact

Please use our issue tracker to report any issues you may encounter when using it. You can also submit feature requests and general help requests via that tracker.

GAP.jl is being maintained by

• Thomas Breuer [email protected]>
• Lars Göttgens [email protected]
• Max Horn [email protected]

License

GAP.jl is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

GAP.jl is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with GAP.jl in form of the file LICENSE, or see https://www.gnu.org/licenses/lgpl.html.

Copyright (C) 2017-2025 by its authors, which include:

• Thomas Breuer
• Sebastian Gutsche
• Lars Göttgens
• Max Horn and many others -- please refer to the git history of the project for a complete list.

Funding

The development of this Julia package is supported by the Deutsche Forschungsgemeinschaft DFG within the Collaborative Research Center TRR 195. The package belongs to the OSCAR project.