diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/GF/Speech/TransformCFG.hs | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/src/GF/Speech/TransformCFG.hs b/src/GF/Speech/TransformCFG.hs index f687e86df..af64f3a89 100644 --- a/src/GF/Speech/TransformCFG.hs +++ b/src/GF/Speech/TransformCFG.hs @@ -89,9 +89,17 @@ stateGFCC = mkGFCC . mkCanon2gfcc . stateGrammarST -- * Grammar filtering -- | Removes all directly and indirectly cyclic productions. +-- FIXME: this may be too aggressive, only one production +-- needs to be removed to break a given cycle. But which +-- one should we pick? +-- FIXME: Does not (yet) remove productions which are cyclic +-- because of empty productions. removeCycles :: CFRules -> CFRules -removeCycles = groupProds . removeCycles_ . ungroupProds - where removeCycles_ rs = [r | r@(CFRule c rhs _) <- rs, rhs /= [Cat c]] +removeCycles = groupProds . f . ungroupProds + where f rs = filter (not . isCycle) rs + where alias = transitiveClosure $ mkRel [(c,c') | CFRule c [Cat c'] _ <- rs] + isCycle (CFRule c [Cat c'] _) = isRelatedTo alias c' c + isCycle _ = False -- | Removes productions which use categories which have no productions. -- Only does one pass through the grammar. |