Safe Haskell	None
Language	Haskell2010

Bluefin.Capability.Tell

Contents

Capability
Handlers
Effectful operations

Synopsis

type Tell = Writer
runTell :: forall w (es :: Effects) r. Monoid w => (forall (e :: Effects). Tell w e -> Eff (e :& es) r) -> Eff es (r, w)
execTell :: forall w (es :: Effects) r. Monoid w => (forall (e :: Effects). Tell w e -> Eff (e :& es) r) -> Eff es w
tell :: forall (e :: Effects) (es :: Effects) w. e <: es => Writer w e -> w -> Eff es ()

Documentation

In most cases you'll probably prefer Yield to Tell, but Tell can still be useful in some cases, for example with Data.Monoid.Any to determine whether an event ever occurred.

Capability

type Tell = Writer #

Handlers

runTell #

Arguments

:: forall w (es :: Effects) r. Monoid w
=> (forall (e :: Effects). Tell w e -> Eff (e :& es) r)	͘
-> Eff es (r, w)

>>> getAny $ snd $ runPureEff $ runTell $ \w -> do
      -- Non-empty list (the tell event does happen)
      for_ [1 .. 10] $ \_ -> tell w (Any True)
True

execTell #

Arguments

:: forall w (es :: Effects) r. Monoid w
=> (forall (e :: Effects). Tell w e -> Eff (e :& es) r)	͘
-> Eff es w

>>> getAny $ runPureEff $ execTell $ \w -> do
      -- Non-empty list (the tell event does happen)
      for_ [1 .. 10] $ \_ -> tell w (Any True)
True

>>> getAny $ runPureEff $ execTell $ \w -> do
      -- Empty list (the tell event does not happen)
      for_ [] $ \_ -> tell w (Any True)
False

Effectful operations

tell #

Arguments

:: forall (e :: Effects) (es :: Effects) w. e <: es
=> Writer w e
-> w	͘
-> Eff es ()

>>> getAny $ runPureEff $ execWriter $ \w -> do
      -- Non-empty list (the tell event does happen)
      for_ [1 .. 10] $ \_ -> tell w (Any True)
True