Haskell GTD DSL

Recently I was looking for software for GTD , or in Russian “how to put things in order” . Of course, many tools are beautiful and simple, but they lack flexibility and customization capabilities. Others are complex monsters with a mountain of unnecessary functionality. How to combine unlimited flexibility with simplicity?

I, as a lover of text interfaces, preferred a domain-specific DSL language instead of a GUI . But writing a language parser from scratch is far from easy. It is much more pleasant to add types over a ready-made Haskell language .


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  data Status
     = Not done
     |  Done
     |  Made by

 data of the month
     = January
     |  February
     |  Martha
     |  April
     |  May
     |  June
     |  July
     |  Augusta
     |  September
     |  October
     |  November
     |  December

 data Date = Date Integer Month Integer

 data When
     = WhenBy
     |  From Date
     |  By date
     |  Between Date Date
     |  Age Integer

 data to
     = Work
     |  Home
     |  To customer
     |  On the resort
     |  In the shop

 data Whom
     = Son
     |  Daughter
     |  Children Integer

 data Nakom
     = Unknown
     |  Vera
     |  Katya
     |  Masha

 data What
     = Tree
     |  House
     |  Liver
     |  Company
     |  Factory
     |  School
     |  Kindergarten
     |  University
     |  Treasure

 data Which Document
     = Contract
     |  Will
     |  Contract
     |  Diploma

 data Holiday
     = New Year
     |  Birthday

 data WhatMake
     = To be born
     |  Die
     |  Marry Nick
     |  To give birth to Whom
     |  Plant what
     |  Build What
     |  Finish what
     |  Find What
     |  Arrange What
     |  Buy What
     |  Sell ​​What
     |  Sign What Document
     |  Earn Integer
     |  Celebrate the Holiday
    
     |  Go where
     |  Go where
     |  Fly off
     |  Go where

 data Project
     = Project String [Project]
     |  Action WhatMake When Status

 life :: Project
 life = Project "Life" [
     Action To be born (Age 0) Made,
     Project "Education" [
         Action (Graduate School) (Age 16) Done,
         Action (Graduate University) (Age 20) Done
         ],
     Project "Family" [
         Action (Marry Unknown) WhenNibbe Done,
         Action (To give birth to a Son) When There Is Not Done,
         Action (Give birth to Daughter) When There Is No Made,
         Action (Give birth (Children 1)) WhenNothing is Done
         ],
     Project "Work" [
         Action (Sign a Contract) When There Is No Made,
         Action (Earn $ foldr (*) 1 [1..20]) WhenNib Be Done
     ],
     Project "Rest" [
         Action (Celebrate New Year) (Between (Date December 31, 2009) (Date January 4, 2010)) Done
     ],
     Action To Die When Never Made
     ]

 Universe :: Project
 universe = "Everything Else" project (repeat universe)

 - the project is completed when all its actions are completed
 completed :: Project -> Bool
 completed (Action _ _ Done) = True
 completed (Project _ list) = all list completed
 completed _ = False

 - nbgf ghbrjk
 Answer :: Project -> Integer
 answer _ = 42

File upload in ghci interpreter

 GHCi, version 6.8.2: http://www.haskell.org/ghc/:?  for help
 Loading package base ... linking ... done.
 Prelude>: l now / gtd / gtd.hs
 [1 of 1] Compiling Main (now / gtd / gtd.hs, interpreted)
 Ok, modules loaded: Main.
 * Main> answer is life
 42
 * Main> Universe Answer
 42
 * Main> completed life
 False
 * Main> Completed Universe
 *** Exception: stack overflow
 * Main> 

shows that the Universe is bigger than the stack :)

I would like to know what queries or reports to the GTD tool would be useful to you?