Add execWriterT #23
Add execWriterT #23
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| @@ -13,6 +13,9 @@ newtype WriterT w m a = WriterT (m (Tuple a w)) | |||
| runWriterT :: forall w m a. WriterT w m a -> m (Tuple a w) | |||
| runWriterT (WriterT x) = x | |||
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| execWriterT :: forall w m a. (Monad m) => WriterT w m a -> m w | |||
| execWriterT m = runWriterT m >>= \(Tuple _ w) -> return w | |||
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How about just snd <$> runWriterT m which only needs an Apply constraint.
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Funny, I actually originally committed it with Apply and <$>, but I looked at existing code and saw that it used Monad so I decided to stick with convention. Given this information, should I go with Apply, and additionally would you like the following code updated to use Apply as well?
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Generally, I'm in favour of using the most general type signatures we can. A lot of this was ported from Haskell, I think, so it can definitely be refined with our new hierarchy.
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Well it would only need Functor right? But couldn't we eschew the constraint entirely with pattern matching? Or is there some law which makes the constraint necessary?
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Sorry about the delay. Let me know what you think of these updates. |
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