Issue with blaze-html

[maxigit]

I'm not sure if its a Vector issue or a blaze-html one, but there is something weird.
Basically I'm trying to convert a vector to html.
If I use Vector.mapM_ or Vector.forM_ it compiles but blows up , if I convert the vector to a list and use mapM_, everything is fine.
I assume that Vector.forM_ should be functionally equivalent to forM_.V.toList but it's not (therefore I think it's a Data.Vector problem ;-))

Here is a way to reproduce problem:

 {-# LANGUAGE OverloadedStrings #-}
  module Main where

  import Control.Monad (forM_)
  import qualified Data.ByteString.Lazy as BL
  import qualified Data.Vector as V

  import qualified Text.Blaze.Html5 as H
  import qualified Text.Blaze.Html.Renderer.String as R


  v :: V.Vector Int
  v = V.fromList [1..10]

  html :: H.Html
  html = V.forM_ v H.toHtml

  vForM_ = forM_ . V.toList

  html' :: H.Html
  html' = vForM_ v H.toHtml

 main = do
     putStrLn  $     R.renderHtml html'
     putStrLn "^ ok"
     putStr  $     R.renderHtml html
     putStrLn "^ ok"

[gregorycollins]

The blaze-html monad instance is not valid:

instance Monad MarkupM where
    return _ = Empty
    {-# INLINE return #-}
    (>>) = Append
    {-# INLINE (>>) #-}
    h1 >>= f = h1 >> f
        (error "Text.Blaze.Internal.MarkupM: invalid use of monadic bind")
    {-# INLINE (>>=) #-}

Not sure why vector's forM_ calls bind but your issue is probably with blaze.

[maxigit]

Maybe Vector.forM_ shouldn't call bind then (as Control.Monad.forM_) doesn't ?

[gregorycollins]

Vector is within its rights to call bind, because a >> b === a >>= \_ -> b by the monad laws.

[maxigit]

Fair enough.

On 27 March 2014 15:58, Gregory Collins notifications@github.com wrote:

Vector is within its rights to call bind, because a >> b === a >>= _ -> bby the monad laws.

Reply to this email directly or view it on GitHubhttps://github.com//issues/13#issuecomment-38822858
.