Avoid stack overflow in ggenString

Libraries/Gast/Gen.dcl

@@ -54,7 +54,7 @@ genState :: GenState
  * @param A list of random numbers (e.g. aStream)
  * @result An inifinite list of strings
  */
-ggenString :: Int Real Int Int RandomStream -> [String]
+ggenString :: !Int !Real !Int !Int !RandomStream -> [String]
 
 derive ggen Int, Bool, Real, Char, String
 derive ggen UNIT, PAIR, EITHER, CONS of gcd, OBJECT of gtd, FIELD of d, RECORD of grd

Libraries/Gast/Gen.icl

@@ -194,17 +194,18 @@ where
         Nothing    -> f s
         Just limit -> take limit $ f s
 
-ggenString :: Int Real Int Int RandomStream -> [String]
+ggenString :: !Int !Real !Int !Int !RandomStream -> [String]
 ggenString maxlen factor minchar maxchar stream = rndStrings stream
 where
 	rndStrings [len:rnd] 
 		# len = toInt ((randIntToReal len) ^ factor * (fromInt maxlen - 0.5))
-		# (chars,rnd)	= seqList (repeatn len genElem) rnd
+		# (chars,rnd)	= genElems [] len rnd
 		  string		= {c \\ c<-chars}
 		= [string:rndStrings rnd]
 	where
-		genElem :: RandomStream -> .(Char, RandomStream)
-		genElem [r:rnd] = (toChar (minchar+((abs r) rem (maxchar+1-minchar))), rnd)
+		genElems :: ![Char] !Int !RandomStream -> (![Char], !RandomStream)
+		genElems cs 0 rnd     = (cs,rnd)
+		genElems cs n [r:rnd] = genElems [toChar (minchar+((abs r) rem (maxchar+1-minchar))):cs] (n-1) rnd
 
 		randIntToReal :: Int -> Real
 		randIntToReal x = (toReal x + if (x >= 0) 0.0 4294967296.0) / 4294967295.0