Wrap filter type more

src/GEval/Core.hs

@@ -377,7 +377,7 @@ checkAndGetDataSources forceInput gevalSpec = do
         challengeDataSourceExpected = expectedSource,
         challengeDataSourceSelector = mSelector,
         challengeDataSourcePreprocess = preprocess,
-        challengeDataSourceFilter = Filter Nothing,
+        challengeDataSourceFilter = noFilter,
         challengeDataSourceInHeader = mInHeader,
         challengeDataSourceOutHeader = mOutHeader }
 
@@ -502,7 +502,7 @@ gevalCoreOnSingleLines metric preprocess inpDecoder inpLine expDecoder expLine o
                            then preprocess
                            else id
         lsSpec = LineSourcesSpecification {
-          lineSourcesFilter = Filter Nothing,
+          lineSourcesFilter = noFilter,
           lineSourcesInputSource = singleLineAsLineSource inpLine inpDecoder preprocess,
           lineSourcesExpectedSource = singleLineAsLineSource expLine expDecoder outputPreprocess,
           lineSourcesOutputSource = singleLineAsLineSource outLine outDecoder outputPreprocess }

src/GEval/DataSource.hs

@@ -1,7 +1,9 @@
 module GEval.DataSource
   (ChallengeDataSource(..),
    DataSource(..),
-   Filter(..))
+   Filter,
+   noFilter,
+   applyFilter)
   where
 
 import Data.Text
@@ -12,6 +14,13 @@ import GEval.Selector
 
 newtype Filter = Filter (Maybe (Text -> Bool))
 
+noFilter :: Filter
+noFilter = Filter Nothing
+
+applyFilter :: Filter -> (Text, (Text, Text)) -> Bool
+applyFilter (Filter Nothing) _ = True
+applyFilter (Filter (Just fun)) (inp, (exp, out)) = fun inp
+
 -- | This type specifies the way the challenge data (input and
 -- expected data, but not outputs) flow into evaluation.
 --