randiso: fix CodePcGroup for trivial gp (#1664)

gap-system · Sep 6, 2017 · 43907fc · 43907fc
1 parent a4b3595
commit 43907fc
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diff --git a/lib/randiso.gi b/lib/randiso.gi
@@ -240,6 +240,9 @@ InstallGlobalFunction( CodePcgs, function( pcgs )
 
     # basic structures
     l := Length( pcgs );
+    if l = 0 then
+      return 0;
+    fi;
     indices := RelativeOrders( pcgs );
     mi := Maximum( indices ) - 1;
     code := 0;

diff --git a/tst/testbugfix/2017-09-06-CodePcGroup.tst b/tst/testbugfix/2017-09-06-CodePcGroup.tst
@@ -0,0 +1,7 @@
+# Issue #1664 on github.com/gap-system/gap
+gap> G := TrivialGroup(IsPcGroup);
+<pc group of size 1 with 0 generators>
+gap> CodePcGroup(G);
+0
+gap> IsTrivial(PcGroupCode(0, 1));
+true