Safe Haskell	None
Language	Haskell2010

Bluefin.Capability.Ask

Contents

Capability
Handlers
Effectful operations

Synopsis

type Ask = Reader
runAsk :: forall r (es :: Effects) a. r -> (forall (e :: Effects). Ask r e -> Eff (e :& es) a) -> Eff es a
ask :: forall (e :: Effects) (es :: Effects) r. e <: es => Reader r e -> Eff es r
asks :: forall (e :: Effects) (es :: Effects) r a. e <: es => Reader r e -> (r -> a) -> Eff es a
local :: forall (e1 :: Effects) (es :: Effects) r a. e1 <: es => Reader r e1 -> (r -> r) -> Eff es a -> Eff es a

Documentation

Ask is Bluefin's version of the Control.Monad.Trans.Reader monad. local allows you to locally override the asked value in a well-scoped way. The original value will be restored when you exit the local block regardless of whether the exit was normal or via an exception.

Capability

type Ask = Reader #

Handlers

runAsk #

Arguments

:: forall r (es :: Effects) a. r	Initial value for `Ask`.
-> (forall (e :: Effects). Ask r e -> Eff (e :& es) a)
-> Eff es a

Effectful operations

ask #

Arguments

:: forall (e :: Effects) (es :: Effects) r. e <: es
=> Reader r e	͘
-> Eff es r

Read the value. Note that ask has the property that these two operations are always equivalent:

do
  r1 <- ask re
  r2 <- ask re
  pure (r1, r2)

do
  r <- ask re
  pure (r, r)

asks #

Arguments

:: forall (e :: Effects) (es :: Effects) r a. e <: es
=> Reader r e
-> (r -> a)	Read the value modified by this function
-> Eff es a

Read the value modified by a function

local #

Arguments

:: forall (e1 :: Effects) (es :: Effects) r a. e1 <: es
=> Reader r e1
-> (r -> r)	In the body, the reader value is modified by this function.
-> Eff es a	Body
-> Eff es a

Locally override the value in the Reader. It will be restored when the local block ends.