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Solid: A functional scripting environment

Solid is a modern remix of (GHC) Haskell with a focus on productivity and joy for programmers.

git clone [email protected]:sol/solid.git
cd solid
cabal install

#!/usr/bin/env solid

names :: [String]
names = ["Jane", "Joe"]

main :: IO ()
main = do
  name <- names.randomChoice
  stdout.writeLine "Hey {name} 👋"

-- or point-free
main :: IO ()
main = stdout.writeLine . "Hey {} 👋" =<< names.randomChoice

$ solid main.hs
Hey Jane 👋

or

$ chmod +x main.hs
$ ./main.hs
Hey Joe 👋

An introduction to Solid for Haskell programmers

Read: book/README.md

Tooling

solid installs GHC 9.10.1 to a private location. It does not use any system provided GHC.

solid caches packages in ~/.local/state/solid/store/. It does not use the user-global cabal store.

Haskell Language Server (LSP) support

It is possible to use Haskell Language Server to get LSP diagnostics while developing a script. This requires the following configuration file next to your script:

# hie.yaml
cradle:
  bios:
    shell: "solid ghc-options $HIE_BIOS_ARG > $HIE_BIOS_OUTPUT"

Using third-party tools

You can use third-party tools that expect GHC options with solid.

Example:

# start a GHCi session
$ solid with ghci main.hs

# run doctest
$ solid with doctest main.hs

# run sensei
$ solid with sensei main.hs

solid with does two things:

1. It puts a suitable version of GHC on the PATH
2. It calls the specified executable with all required GHC options

Running doctest

solid with can be used to run doctest. However, this only works if a suitable version of doctest is available on the PATH. solid doctest provides a more robust way to run doctest.

Example:

$ solid doctest main.hs

Specifying additional dependencies

As of now, solid does not provide a mechanism to manage third-party dependencies. This limitation will be lifted eventually.

However, solid accepts arbitrary GHC options, including -package, which can be used to specify arbitrary additional Haskell dependencies.

Example:

$ solid with ghci -package=hspec -package=QuickCheck test/Spec.hs

Note that for this to work, a version of the requested package has to be present in the cabal store. If a package is not yet in the cabal store, then you have to populate the cabal store manually, e.g. with cabal repl --build-depends.

Example:

$ echo | cabal repl --build-depends hspec,QuickCheck

Notable differences from Haskell

This section lists semantic differences from Haskell that are not caught by the type system.

• ByteString.strip and ByteString.words only consider ASCII spaces. This has the advantage that they can be safely used on UTF-8 input. (unlike their counterparts in Data.ByteString.Char8)

Limitations

• The where in module ... where has to be followed by a newline, e.g. this is not supported:

  module Foo where bar :: Int
                   bar = 23