Faster regular expression pattern matching in the grammar compiler.

The sequence operator (x+y) was implemented by splitting the string to be
matched at all positions and trying to match the parts against the two
subpatterns. To reduce the number of splits, we now estimate the minimum and
maximum length of the string that the subpatterns could match. For common
cases, where one of the subpatterns is a string of known length, like
in (x+"y") or (x + ("a"|"o"|"u"|"e")+"y"), only one split will be tried.

src/compiler/GF/Compile/Compute/ConcreteNew.hs

@@ -8,7 +8,7 @@ module GF.Compile.Compute.ConcreteNew
 import GF.Grammar hiding (Env, VGen, VApp, VRecType)
 import GF.Grammar.Lookup(lookupResDefLoc,allParamValues)
 import GF.Grammar.Predef(cPredef,cErrorType,cTok,cStr)
-import GF.Grammar.PatternMatch(matchPattern)
+import GF.Grammar.PatternMatch(matchPattern,measurePatt)
 import GF.Grammar.Lockfield(unlockRecord,lockLabel,isLockLabel,lockRecType)
 import GF.Compile.Compute.Value hiding (Predefined(..))
 import GF.Compile.Compute.Predef(predef,predefName,delta)
@@ -320,7 +320,7 @@ valueTable env i cs =
               TWild _ -> True
               _ -> False
 
-    valueCase (p,t) = do p' <- inlinePattMacro p
+    valueCase (p,t) = do p' <- measurePatt # inlinePattMacro p
                          let pvs = pattVars p'
                          vt <- value (extend pvs env) t
                          return (p', \ vs -> Bind $ \ bs -> vt (push' p' bs pvs vs))