Safe Haskell	Safe
Language	Haskell2010

Env.Internal.Error

Description

This module contains an extensible error infrastructure.

Each kind of errors gets a separate type class which encodes a Prism (roughly a getter and a constructor). The Readers, then, have the constraints for precisely the set of errors they can return.

Synopsis

data Error
- = UnsetError
- | EmptyError
- | UnreadError String
class AsUnset e where
class AsEmpty e where
class AsUnread e where

Documentation

data Error Source #

The type of errors returned by envparse's Readers. These fall into 3 categories:

Variables that are unset in the environment.
Variables whose value is empty.
Variables whose value cannot be parsed using the Read instance.

Constructors

UnsetError
EmptyError
UnreadError String

Instances

Eq Error Source #
Instance details Defined in Env.Internal.Error Methods (==) :: Error -> Error -> Bool # (/=) :: Error -> Error -> Bool #
Show Error Source #
Instance details Defined in Env.Internal.Error Methods showsPrec :: Int -> Error -> ShowS # show :: Error -> String # showList :: [Error] -> ShowS #
AsUnread Error Source #
Instance details Defined in Env.Internal.Error Methods unread :: String -> Error Source # tryUnread :: Error -> Maybe String Source #
AsEmpty Error Source #
Instance details Defined in Env.Internal.Error Methods empty :: Error Source # tryEmpty :: Error -> Maybe () Source #
AsUnset Error Source #
Instance details Defined in Env.Internal.Error Methods unset :: Error Source # tryUnset :: Error -> Maybe () Source #

class AsUnset e where Source #

The class of types that contain and can be constructed from the error returned from parsing unset variables.

Minimal complete definition

unset, tryUnset

Methods

unset :: e Source #

tryUnset :: e -> Maybe () Source #

Instances

AsUnset Error Source #
Instance details Defined in Env.Internal.Error Methods unset :: Error Source # tryUnset :: Error -> Maybe () Source #

class AsEmpty e where Source #

The class of types that contain and can be constructed from the error returned from parsing variables whose value is empty.

Minimal complete definition

empty, tryEmpty

Methods

empty :: e Source #

tryEmpty :: e -> Maybe () Source #

Instances

AsEmpty Error Source #
Instance details Defined in Env.Internal.Error Methods empty :: Error Source # tryEmpty :: Error -> Maybe () Source #

class AsUnread e where Source #

The class of types that contain and can be constructed from the error returned from parsing variable whose value cannot be parsed using the Read instance.

Minimal complete definition

unread, tryUnread

Methods

unread :: String -> e Source #

tryUnread :: e -> Maybe String Source #

Instances

AsUnread Error Source #
Instance details Defined in Env.Internal.Error Methods unread :: String -> Error Source # tryUnread :: Error -> Maybe String Source #