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

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
Show Error Source
AsUnread Error Source
AsEmpty Error Source
AsUnset Error Source

class AsUnset e where Source

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

Methods

unset :: e Source

tryUnset :: e -> Maybe () Source

Instances

AsUnset Error 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.

Methods

empty :: e Source

tryEmpty :: e -> Maybe () Source

Instances

AsEmpty Error 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.

Methods

unread :: String -> e Source

tryUnread :: e -> Maybe String Source

Instances

AsUnread Error Source