Hello, There is a nice code for computing Farey symbols of arithmetic groups (see [1] and [2]). My question is about implementation. There are basically two ways of describing a subgroup of SL(2,Z). Either by providing a membership test (ie a __contains__ method) or by giving a Shreier graph for some system of generators. The former implementation is used for congruence subgroups while the latter provides a way to describe any arithmetic group (see sage.modular.arithgroup.arithgroup_perm).
The current implementation of Farey symbols relies on membership test which costs a lot for a group given by its Shreier graph (we first decompose the matrix in standard generators of SL(2,Z) via continued fraction and then test if the word is a loop in the Shreier graph). My question is whether it is possible to adapt the current implementation of the computation of Farey symbols to the case of a group given by its Shreier graph ? Best, Vincent [1] http://trac.sagemath.org/sage_trac/ticket/11709 [2] http://trac.sagemath.org/sage_trac/ticket/11875 -- -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
