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Parse environment variables Here's a simple example of a program that uses envparse's parser:

module Main (main) where

import Control.Monad (unless)
import Env

data Hello = Hello { name :: String, quiet :: Bool }

hello :: IO Hello
hello = Env.parse (header "envparse example") $
Hello <$> var (str <=< nonempty) "NAME"  (help "Target for the greeting")
<*> switch                 "QUIET" (help "Whether to actually print the greeting")

main :: IO ()
main = do
Hello {name, quiet} <- hello
unless quiet $
putStrLn ("Hello, " ++ name ++ "!")

The NAME environment variable is mandatory and contains the name of the person to greet. QUIET, on the other hand, is an optional boolean flag, false by default, that decides whether the greeting should be silent. If the NAME variable is undefined in the environment then running the program will result in the following help text:

envparse example

Available environment variables:

NAME                   Target for the greeting
QUIET                  Whether to actually print the
greeting

Parsing errors:

NAME is unset

package envy

An environmentally friendly way to deal with environment variables For package use information see the README.md
package equivalence

Maintaining an equivalence relation implemented as union-find using STT. This is an implementation of Tarjan's Union-Find algorithm (Robert E. Tarjan. "Efficiency of a Good But Not Linear Set Union Algorithm", JACM 22(2), 1975) in order to maintain an equivalence relation. This implementation is a port of the union-find package using the ST monad transformer (instead of the IO monad).
package error-or

Composable, hierarchical errors. An Applicative Functor with error accumulation. Built in tree like error type meant for gathering and reporting errors to users.
package executable-path

Finding out the full path of the executable. The documentation of "System.Environment.getProgName" says that "However, this is hard-to-impossible to implement on some non-Unix OSes, so instead, for maximum portability, we just return the leafname of the program as invoked." This library tries to provide the missing path. Note: Since base 4.6.0.0, there is also a function "System.Environment.getExecutablePath".
package extended-reals

Extension of real numbers with positive/negative infinities Extension of real numbers with positive/negative infinities (±∞). It is useful for describing various limiting behaviors in mathematics.
package extractable-singleton

A functor, where the "stored" value is isomorphic to Identity A functor, where the "stored" value is isomorphic to Identity
package fakedata

Library for producing fake data Please see the README on GitHub at https://github.com/psibi/fakedata#readme
package fakedata-parser

Please see the README on GitHub at https://github.com/psibi/fakedata-parser#readme
package fakepull

Monad to pull from fake stream-like objects. See https://github.com/igrep/haskell-fakepull#readme.

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