Merge branch 'master' of github.com:ehwat/subgroup-ladders

2 files changed, 34 insertions, 3 deletions

diff --git a/gap/subgroupladders.autodoc b/gap/subgroupladders.autodoc
new file mode 100644
index 0000000..0e9c8d2
--- /dev/null
+++ b/gap/subgroupladders.autodoc
@@ -0,0 +1,31 @@
+@AutoDocPlainText
+@Chapter Introduction
+
+This package provides an algorithm that computes a subgroup ladder from a permutation group up to the parent symmetric group.
+The algorithm was described by Bernd Schmalz in [1, Theorem 3.1.1].
+
+Solutions of some problems in group theory can relatively easy be transferred to a sub- or supergroup if the index is small.
+Let <M>G</M> be a permutation group on the set <M>\{1,...,n\}</M>.
+So one might try to find a series of subgroups <M>G = H_0,...,H_k = S_n</M> of the symmetric group <M>S_n</M> such that <M>H_{{i-1}}</M> is a subgroup of <M>H_i</M> for every <M>i</M> and transfer the solution of a problem for the symmetric group step by step to <M>G</M>.
+
+Sometimes it is not possible to find such a series with small indices between consecutive subgroups.
+This is where subgroup ladders may make sense:
+A subgroup ladder is series of subgroups <M>G = H_0,...,H_k = S_n</M> of the symmetric group such that for every <M>1 \leq i \leq k</M>, <M>H_i</M> is a subgroup of <M>H_{{i-1}}</M> or <M>H_{{i-1}}</M> is a subgroup of <M>H_i</M>.
+So we sometimes go up to a larger group in order to keep the indices small.
+
+If <M>G</M> is a Young subgroup of <M>S_n</M>, the algorithm in this repository can find a subgroup ladder of <M>G</M> such that the indices are at most the degree of the permutation group.
+
+@Chapter subgroupladders
+@Section subgroupladders
+
+@Chapter License
+
+subgroupladders is free software you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; either version 3 of the License, or (at your option) any later
+version. For details, see the file LICENSE distributed as part of this package
+or see the FSF's own site.
+
+@Chapter References
+[1] B. Schmalz. Verwendung von Untergruppenleitern zur Bestimmung von Doppelnebenklassen. Bayreuther Mathematische Schriften, 31, S.109--143, 1990.
+@EndAutoDocPlainText
diff --git a/gap/subgroupladders.gd b/gap/subgroupladders.gd
index 59b9325..2291eb7 100644
--- a/gap/subgroupladders.gd
+++ b/gap/subgroupladders.gd
@@ -4,14 +4,13 @@
 # Declarations
 #
 
-#! @Chapter subgroup-ladders
-#! @Section subgroup-ladders
-
 #! @Description
 #! Given a list of lists <A>part</A> of positive integers, this will compute 
 #! the Young subgroup corresponding to this partition.
+#! This function does not check whether the supplied lists are actually disjoint. 
 #! @Returns a group
 #! @Arguments part
+#! @ChapterInfo subgroupladders, subgroupladders
 DeclareGlobalFunction( "YoungGroupFromPartition" );
 #! @Description
 #! Given a permutation group <A>G</A>, this will compute a subgroup ladder
@@ -26,4 +25,5 @@ DeclareGlobalFunction( "YoungGroupFromPartition" );
 #! At this step, the index may be larger than the degree.
 #! @Returns a list of groups
 #! @Arguments G
+#! @ChapterInfo subgroupladders, subgroupladders
 DeclareGlobalFunction( "SubgroupLadder");