Dhall is a total programming language tailored for configuration files.
Questions tagged [dhall]
62 questions
11
votes
1 answer
Can the type of valid graphs be encoded in Dhall?
I'd like to represent a wiki (a set of documents comprising a directed graph) in Dhall. These documents will be rendered to HTML, and I'd like to prevent broken links from ever being generated. As I see it, this could be accomplished either by…
Bjørn Westergard
- 113
- 6
11
votes
1 answer
How do I represent a tuple in dhall?
I would like to represent IPv4 addresses in dhall, so I can manage my host configurations.
By default, this is held as Text; but that's clearly unsatisfactory as it allows any old text to slip through. I would like to keep these values as a 4-tuple…
user3416536
- 1,429
- 9
- 20
6
votes
1 answer
Splitting a string in dhall
I'm playing with dhall and wondered how I can implement a string splitting function of the form
λ(text: Text) -> λ(delimiter: Text) -> List Text
However, it appears dhall has no concept/type to represent individual characters. and there's no such…
Johannes Rudolph
- 35,298
- 14
- 114
- 172
6
votes
1 answer
How to define and use a Haskell-like sum type in Dhall
How can I define a sum type analogous to Haskell's sum types in the Dhall programming language?
For instance, if in Haskell I'd define
data SumProp = Option1 | Option2
My purpose is to define in Dhall a record in which one of its properties has a…
Jesuspc
- 1,664
- 10
- 25
5
votes
1 answer
How to create a dhall schema with arbitrary key but typed values?
In dhall, how can I create a schema for the following yaml?
environment:
local:
path: "/path/to/env"
envvars:
- var1
- var2
stage:
path: "/path/to/env"
envvars:
- var1
…
kjq07bd
- 125
- 1
- 4
5
votes
1 answer
Is there a way to generate a dhall schema from an haskell datatype?
I'm trying to rewrite a BIG yaml configuration file used in Haksell applicationusing dhall.
To do so I'm using json-to-dhall which requires a SCHEMA which is the type of the resuting expression. The problem is the actual schema is almost impossible…
mb14
- 22,276
- 7
- 60
- 102
5
votes
1 answer
Difference between `dhall format` and `dhall lint`
Playing with dhall for the first time I saw that it supports these two options:
./dhall --help
...
lint Improve Dhall code
format Formatter for the Dhall language
What's the difference between the two?…
Johannes Rudolph
- 35,298
- 14
- 114
- 172
4
votes
1 answer
How to use polymorphic type constructors in dhall
I am trying to define a polymorphic type in Dhall. In Haskell it would look like:
data MyType a = Some a | SomethingElse
To do so I have defined this function in Dhall (mkMyType.dhall):
let SomethingElse = ./SomethingElse.dhall in λ(a : Type) → <…
Jesuspc
- 1,664
- 10
- 25
3
votes
2 answers
Integer division in Dhall
I would like to compute the quotient of two Naturals. The requirement I need to fulfill is that I have a few configuration items that must be dynamically defined as shares of another (i.e. one container has X memory, two configuration keys for the…
stefanobaghino
- 11,253
- 4
- 35
- 63
3
votes
1 answer
How to write a function that handles a Union type in Dhall
I'm trying to wrap my head around how programming works in Dhall. Consider the following union type:
let Object = < NoId | WithId : Text >
I want to write a function extractId that returns an Optional Text containing the Id (or None), but I can't…
Julian Stecklina
- 1,271
- 1
- 10
- 24
3
votes
1 answer
Dynamic records key type
I'm trying to generate some YAML containing a map with dynamic keys, as described here. This works if I use Text keys, but not when the keys have any other type. I'd like to use a union type for the keys if possible.
I've tried using different types…
DaveWM
- 56
- 3
3
votes
1 answer
How to represent "Data.Map Text Text" in Dhall?
If I have a type in Haskell like this:
data MyType = MyType
{ env :: Map Text Text
}
How can I represent a value of MyType in Dhall?
{ env = ???
}
What I want to do is to write values of MyType in Dhall and then read it in from Haskell and…
Linus Arver
- 1,331
- 1
- 13
- 18
2
votes
1 answer
Gradual typing in Dhall
The Dhall website has a nice example:
{- You can optionally add types
`x : T` means that `x` has type `T`
-}
let Config : Type =
{- What happens if you add another field here? -}
{ home : Text
, privateKey : Text
,…
Felix
- 8,385
- 10
- 40
- 59
2
votes
1 answer
dhall Invalid alternative type
I've defined a union type with two elements like so:
FunctionCode.dhall
{- Function Code union -}
let StaticFC = ./StaticFunctionCode.dhall
let DynamicFC = ./DynamicFunctionCode.dhall
in < Static : StaticFC | Dynamic : DynamicFC >
The two types,…
dangeroushobo
- 1,291
- 2
- 16
- 28
2
votes
1 answer
What is the difference between packages.dhall and spago.dhall files?
spago docs state:
packages.dhall: this file is meant to contain the totality of the packages available to your project (that is, any package you might want to import).
In practice it pulls in the official package-set as a base, and you are then…
bela53
- 3,040
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