withParams*: drop redundant call to 'length' by using 'withArrayLen'

We encode various arrays of the same length through 'withArray'.
Each of these computes the length, so we might as well take the
length from one of these.

Author: robx

src/Database/PostgreSQL/LibPQ.hsc

@@ -756,12 +756,11 @@ withParams params action =
         withMany (maybeWith B.useAsCString) values $ \c_values ->
             withArray c_values $ \vs ->
                 withArray c_lengths $ \ls ->
-                    withArray formats $ \fs ->
-                        action n ts vs ls fs
+                    withArrayLen formats $ \n fs ->
+                        action (toEnum n) ts vs ls fs
   where
     (oids, values, c_lengths, formats) =
         foldl' accum ([],[],[],[]) $ reverse params
-    !n = toEnum $ length params
 
     accum (!a,!b,!c,!d) Nothing = ( invalidOid:a
                                   , Nothing:b
@@ -783,11 +782,10 @@ withParamsPrepared params action =
     withMany (maybeWith B.useAsCString) values $ \c_values ->
         withArray c_values $ \vs ->
             withArray c_lengths $ \ls ->
-                withArray formats $ \fs ->
-                    action n vs ls fs
+                withArrayLen formats $ \n fs ->
+                    action (toEnum n) vs ls fs
   where
     (values, c_lengths, formats) = foldl' accum ([],[],[]) $ reverse params
-    !n = toEnum $ length params
 
     accum (!a,!b,!c) Nothing       = ( Nothing:a
                                      , 0:b