dynamic

Finally, dynamically typed programming in Haskell made easy!

Introduction

Tired of making data types in your Haskell programs just to read and manipulate basic JSON/CSV files? Tired of writing imports? Use dynamic, dynamically typed programming for Haskell!

Load it up

Launch ghci, the interactive REPL for Haskell.

import Dynamic

Now you're ready for dynamicness!

Make dynamic values as easy as pie!

Primitive values are easy via regular literals:

> 1
1
> "Hello, World!"
"Hello, World!"

Arrays and objects have handy functions to make them:

> fromList [1,2]
[
    1,
    2
]
> fromDict [ ("k", 1), ("v", 2) ]
{
    "k": 1,
    "v": 2
}

Get object keys or array or string indexes via !:

> fromDict [ ("k", 1), ("v", 2) ] ! "k"
1
> fromList [1,2] ! 1
2
> "foo" ! 2
"o"

Web requests!

> chris <- getJson "https://api.github.com/users/chrisdone"
> chris
{
    "bio": null,
    "email": null,
    "public_gists": 176,
    "repos_url": "https://api.github.com/users/chrisdone/repos",
    "node_id": "MDQ6VXNlcjExMDE5",
    "following_url": "https://api.github.com/users/chrisdone/following{/other_user}",
    "location": "England",
    "url": "https://api.github.com/users/chrisdone",
    "gravatar_id": "",
    "blog": "https://chrisdone.com",
    "gists_url": "https://api.github.com/users/chrisdone/gists{/gist_id}",
    "following": 0,
    "hireable": null,
    "organizations_url": "https://api.github.com/users/chrisdone/orgs",
    "subscriptions_url": "https://api.github.com/users/chrisdone/subscriptions",
    "name": "Chris Done",
    "company": "FP Complete @fpco ",
    "updated_at": "2019-02-22T11:11:18Z",
    "created_at": "2008-05-21T10:29:09Z",
    "followers": 1095,
    "id": 11019,
    "public_repos": 144,
    "avatar_url": "https://avatars3.githubusercontent.com/u/11019?v=4",
    "type": "User",
    "events_url": "https://api.github.com/users/chrisdone/events{/privacy}",
    "starred_url": "https://api.github.com/users/chrisdone/starred{/owner}{/repo}",
    "login": "chrisdone",
    "received_events_url": "https://api.github.com/users/chrisdone/received_events",
    "site_admin": false,
    "html_url": "https://github.com/chrisdone",
    "followers_url": "https://api.github.com/users/chrisdone/followers"
}

Trivially read CSV files!

> fromCsvNamed "name,age,alive,partner\nabc,123,true,null\nabc,ok,true,true"
[{
    "alive": true,
    "age": 123,
    "partner": null,
    "name": "abc"
},{
    "alive": true,
    "age": "ok",
    "partner": true,
    "name": "abc"
}]

Dynamically typed programming!

Just write code like you do in Python or JavaScript:

> if chris!"followers" > 500 then chris!"public_gists" * 5 else chris!"name"
880

Experience the wonders of dynamic type errors!

Try to treat non-numbers as numbers and you get the expected result:

> map (\o -> o ! "age" * 2) $ fromCsvNamed "name,age,alive,partner\nabc,123,true,null\nabc,ok,true,true"
[246,*** Exception: DynamicTypeError "Couldn't treat string as number: ok"

Laziness makes everything better!

> map (*2) $ toList $ fromJson "[\"1\",true,123]"
[2,*** Exception: DynamicTypeError "Can't treat bool as number."

Woops...

> map (*2) $ toList $ fromJson "[\"1\",123]"
[2,246]

That's better!

Modifying and updating records

Use modify or set to massage data into something more palatable.

> modify "followers" (*20) chris
{
    "bio": null,
    "email": null,
    "public_gists": 176,
    "repos_url": "https://api.github.com/users/chrisdone/repos",
    "node_id": "MDQ6VXNlcjExMDE5",
    "following_url": "https://api.github.com/users/chrisdone/following{/other_user}",
    "location": "England",
    "url": "https://api.github.com/users/chrisdone",
    "gravatar_id": "",
    "blog": "https://chrisdone.com",
    "gists_url": "https://api.github.com/users/chrisdone/gists{/gist_id}",
    "following": 0,
    "hireable": null,
    "organizations_url": "https://api.github.com/users/chrisdone/orgs",
    "subscriptions_url": "https://api.github.com/users/chrisdone/subscriptions",
    "name": "Chris Done",
    "company": "FP Complete @fpco ",
    "updated_at": "2019-02-22T11:11:18Z",
    "created_at": "2008-05-21T10:29:09Z",
    "followers": 21900,
    "id": 11019,
    "public_repos": 144,
    "avatar_url": "https://avatars3.githubusercontent.com/u/11019?v=4",
    "type": "User",
    "events_url": "https://api.github.com/users/chrisdone/events{/privacy}",
    "starred_url": "https://api.github.com/users/chrisdone/starred{/owner}{/repo}",
    "login": "chrisdone",
    "received_events_url": "https://api.github.com/users/chrisdone/received_events",
    "site_admin": false,
    "html_url": "https://github.com/chrisdone",
    "followers_url":
    "https://api.github.com/users/chrisdone/followers"
}

List of numbers?

The answer is: Yes, Haskell can do that!

> [1.. 5] :: [Dynamic]
[1,2,3,4,5]

Coming soon

Monoid instances so we can append Dynamics together!