[1m[4m[31m9. Stallings foldings[0m
[1m[4m[31m9.1 Some theory[0m
[1m[4m[31m9.2 Foldings[0m
A finitely generated subgroup of a finitely generated free group is given
through a list whose first element is the number of generators of the free
group and the remaining elements are the generators of the subgroup.
A generator of the subgroup may be given through a string of letters or
through a list of positive integers as decribed in what follows.
When the free group has n generators, the n+j^th letter of the alphabet
should be used to represent the formal inverse of the j^th generator which
is represented by the j^th letter. The number of generators of the free
group must not exceed 7.
For example, [22m[32m[2,"abc","bbabcd"][0m means the subgroup of the free group on 2
generators generated by aba^-1 and bbaba^-1b^-1. The same subgroup may be
given as [22m[32m[2,[1,2,3],[2,2,1,2,3,4]][0m
[1m[4m[31m9.2-1 FlowerAutomaton[0m
[1m[34m> FlowerAutomaton( [0m[22m[34mL[0m[1m[34m ) _____________________________________________[0mfunction
The argument [22m[32mL[0m is a subgroup of the free group given through any of the
representations described above.
[1m[4m[31m9.2-2 FoldFlowerAutomaton[0m
[1m[34m> FoldFlowerAutomaton( [0m[22m[34mA[0m[1m[34m ) _________________________________________[0mfunction
Makes identifications on the flower automaton [22m[32mA[0m
