purescript-tidy-codegen
Super convenient code-generation for PureScript using purescript-tidy.
Introduction
tidy-codegen provides constructors for quickly building CST types from
purescript-language-cst-parser. Paired with tidy, code-generators can
be assembled in hardly any time at all.
import Prelude
import PureScript.CST.Types
import Tidy.Codegen
import Tidy.Codegen.Monad
import Control.Monad.Writer (tell)
import Data.Maybe (Maybe(..))
import Partial.Unsafe (unsafePartial)
exampleModule :: Module Void
exampleModule = unsafePartial $ codegenModule "Data.Maybe" do
importOpen "Prelude"
tell
[ declData "Maybe" [ typeVar "a" ]
[ dataCtor "Nothing" []
, dataCtor "Just" [ typeVar "a" ]
]
, declDerive Nothing [] "Functor" [ typeCtor "Maybe" ]
, declSignature "maybe" do
typeForall [ typeVar "a", typeVar "b" ] do
typeArrow
[ typeVar "b"
, typeArrow [ typeVar "a" ] (typeVar "b")
, typeApp (typeCtor "Maybe") [ typeVar "a" ]
]
(typeVar "b")
, declValue "maybe" [ binderVar "nothing", binderVar "just" ] do
exprCase [ exprSection ]
[ caseBranch [ binderCtor "Just" [ binderVar "a" ] ] do
exprApp (exprIdent "just") [ exprIdent "a" ]
, caseBranch [ binderCtor "Nothing" [] ] do
exprIdent "nothing"
]
]module Data.Maybe where
import Prelude
data Maybe a = Nothing | Just a
derive instance Functor Maybe
maybe :: forall a b. b -> (a -> b) -> Maybe a -> b
maybe nothing just = case _ of
Just a -> just a
Nothing -> nothingA note on overloading and Partial
tidy-codegen is designed to be fast to write. It features a highly overloaded
API which lets you intuitively construct CST types like it's a bare-bones AST.
It's common to use string and array literals, where the CST types actually use
more specific newtypes or non-empty arrays. In these cases, the overloaded APIs
will do runtime validation (eg. by lexing string literals) and crash if these
arguments are incorrect. This results in a Partial constraint which must be
discharged with unsafePartial. If you want to avoid this partiality, you can
always pass in the safe types instead with all overloaded APIs and no Partial
constraint will be required.
Examples
All of the snapshot modules are self contained examples,
with their results shown in .output files.