Dhall

The YAML killer :)

You:
  Dont:
    Want:
      Me:
        To:
          Write:
            - YAML

1. YAML is only easy to read/write if you use a small subset of it. YAML specs are huge (>20k lines). 9 ways to write multi line string.

2. YAML is not portable (https://matrix.yaml.io/valid.html)

3. Surprising behaviour

- Don Corleone: Do you have faith?
- Clemenza: Yes
- Don Corleone: Do I have your loyalty?

----

python: 3.5.3
postgres: 9.3

----

Effenaar: Eindhoven
013: Tilburg
[{'Don Corleone': 'Do you have faith?'},
 {'Clemenza': True},
 {'Don Corleone': 'Do I have your loyalty?'}]
 
----

{'python': '3.5.3',
 'postgres': 9.3}
 
----

{11: 'Tilburg',
 'Effenaar': 'Eindhoven'}

4. Quickly you roll out your own version of YAML with its own rules.

Why DHALL?

1. Total - Evaluation always terminates and never hangs or infinitely loops

2. Safe - Evaluation never crashes or throws exceptions

3. Distributed - Expressions can reference other expressions by URL or path

4. Strongly normalizing - All expressions (even functions) have a normal form

5. Statically typed - Configurations can be validated ahead-of-time

6. Strongly typed - No coercions, casts or subtyping

7. Built-in data types - Includes lists, anonymous records and anonymous unions

What is DHALL?

Think of it as:

JSON

+

functions

+

types

+

imports

{ home = "/home/rok"
, privateKey = "/home/rok/.ssh/id_rsa"
, publicKey = "/home/rok/.ssh/id_rsa.pub"
}
let mkUser = \(user : Text) ->
  { home = "/home/${user}"
  , privateKey = "/home/${user}/.ssh/id_rsa"
  , publicKey = "/home/${user}/.ssh/id_rsa.pub"
  }
in mkUser "rok"
Let User : Type =
 { home : Text
 , privateKey : Text
 , publicKey : Text
 }
let mkUser : Text -> User = \(user : Text) ->
  { home = "/home/${user}"
  , privateKey = "/home/${user}/.ssh/id_rsa"
  , publicKey = "/home/${user}/.ssh/id_rsa.pub"
  }
in mkUser "rok" : User
...
let generate = https://prelude.dhall-lang.org/List/generate
in generate 10 User (\index : Natural -> mkUser "build${Natural/show index}")

DEMO

Integrations

Bidnings

Output formats

Libraries

Editor integration:

Thank you

DhallDhall

By Rok Garbas

DhallDhall

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