From 47dedcf256976495f405a802920fa3012f683a52 Mon Sep 17 00:00:00 2001
From: bringert <bringert@cs.chalmers.se>
Date: Thu, 13 Apr 2006 14:18:13 +0000
Subject: [PATCH] Fixed bug in SRG top-down filtering where the start category
 would be removed if it wasn't referenced by itself.

---
 src/GF/Speech/SRG.hs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/GF/Speech/SRG.hs b/src/GF/Speech/SRG.hs
index 0334c1301..8080b941f 100644
--- a/src/GF/Speech/SRG.hs
+++ b/src/GF/Speech/SRG.hs
@@ -140,7 +140,11 @@ topDownFilter srg@(SRG { startCat = start, rules = rs }) = srg { rules = rs' }
   rhsCats = [ (c,c') | r@(SRGRule c _ ps) <- rs, 
                        SRGAlt _ _ ss <- ps, 
                        c' <- filterCats ss]
-  keep = allRelated (transitiveClosure $ mkRel rhsCats) start
+  uses = reflexiveClosure_ (allSRGCats srg) $ transitiveClosure $ mkRel rhsCats
+  keep = allRelated uses start
+
+allSRGCats :: SRG -> [String]
+allSRGCats SRG { rules = rs } = [c | SRGRule c _ _ <- rs]
 
 --
 -- * Utilities for building and printing SRGs