@@ -37,6 +37,15 @@
3737-- on stream types can be as efficient as transformations on 'Fold' (e.g.
3838-- 'Streamly.Internal.Data.Fold.lmap').
3939--
40+-- = Left folds vs Right Folds
41+--
42+-- The folds in this module are left folds, therefore, even partial folds, e.g.
43+-- @head@ in this module, would drain the whole stream. On the other hand, the
44+-- partial folds in "Streamly.Prelude" module are lazy right folds and would
45+-- terminate as soon as the result is determined. However, the folds in this
46+-- module can be composed but the folds in "Streamly.Prelude" cannot be
47+-- composed.
48+--
4049-- = Programmer Notes
4150--
4251-- > import qualified Streamly.Data.Fold as FL