Language.PureScript.Bridge.Builder

A bridge builder DSL, powered by Monad, Alternative and lens.

Bridges can be built within the BridgeBuilder monad. You can check properties of the to-be-bridged HaskellType with ^== or doCheck, you have choice (<|>), you can fail (empty) and you can return a translated PSType (return). The HaskellType can be accessed with:

view haskType

Find usage examples in Language.PureScript.Bridge.Primitives and Language.PureScript.Bridge.PSTypes

Documentation

data BridgeBuilder a

Instances

Monad BridgeBuilder

Functor BridgeBuilder

Applicative BridgeBuilder

Alternative BridgeBuilder

Alternative instance for BridgeBuilder so you can construct bridges with <|>, which behaves like a logical or (||). If the left-hand side results in Nothing the right-hand side is used, otherwise the left-hand side. For usage examples see Language.PureScript.Bridge.Primitives.

MonadPlus BridgeBuilder

MonadReader BridgeData BridgeBuilder

type BridgePart = BridgeBuilder PSType

data FixUpBuilder a

Bridges to use when a BridgePart returns Nothing (See buildBridgeWithCustomFixUp).

It is similar to BridgeBuilder but does not offer choice or failure. It is used for constructing fallbacks if a BridgePart evaluates to Nothing.

For type definitions you should use the more generic (MonadReader BridgeData m) constraint. This way your code will work in both FixUpBuilder and BridgeBuilder:

{-# LANGUAGE FlexibleContexts #-}

import           Control.Monad.Reader.Class
import           Language.PureScript.Bridge.TypeInfo

Instances

Monad FixUpBuilder

Functor FixUpBuilder

Applicative FixUpBuilder

MonadReader BridgeData FixUpBuilder

type FixUpBridge = FixUpBuilder PSType

data BridgeData

Instances

HasHaskType BridgeData

By implementing the haskType lens in the HasHaskType class, we are able to use it for both BridgeData and a plain HaskellType, therefore you can use it with doCheck and ^== for checks on the complete HaskellType value.

Example:

stringBridge :: BridgePart
stringBridge = do
  -- Note: we are using the HaskellType instance here:
  haskType ^== mkTypeInfo (Proxy :: Proxy String)
  return psString

MonadReader BridgeData FixUpBuilder

MonadReader BridgeData BridgeBuilder

fullBridge :: Lens' BridgeData FullBridge

Lens for access to the complete bridge from within our Reader monad.

This is used for example for implementing psTypeParameters.

(^==) :: Eq a => Getter HaskellType a -> a -> BridgeBuilder () infix 4

Check parts of haskType for equality:

textBridge :: BridgePart
textBridge = do
  typeName ^== "Text"
  typeModule ^== "Data.Text.Internal" <|> typeModule ^== "Data.Text.Internal.Lazy"
  return psString

doCheck :: Getter HaskellType a -> (a -> Bool) -> BridgeBuilder ()

Do some check on properties of haskType.

(<|>) :: Alternative f => forall a. f a -> f a -> f a

An associative binary operation

psTypeParameters :: MonadReader BridgeData m => m [PSType]

Bridge haskType typeParameters over to PureScript types.

To be used for bridging type constructors.

type FullBridge = HaskellType -> PSType

buildBridge :: BridgePart -> FullBridge

Build a bridge.

This is a convenience wrapper for buildBridgeWithCustomFixUp and should normally be sufficient.

Definition:

buildBridgeWithCustomFixUp clearPackageFixUp

clearPackageFixUp :: MonadReader BridgeData m => m PSType

Bridge to PureScript by simply clearing out the _typePackage field. This bridge is used by default as FixUpBridge by buildBridge:

buildBridge = buildBridgeWithCustomFixUp clearPackageFixUp

Thus, if no bridge matches a type, it gets optimistically translated to a PureScript type which is idential to the Haskell type. Only the _typePackage field gets cleared, as it is very unlikely that the PureScript package is called the same as the Haskell package.

Alternatively, if you are not that optimistic, you can use errorFixUp - which simply calls error when used.

buildBridgeWithCustomFixUp errorFixUp yourBridge

Of course you can also write your own FixUpBridge. It works the same as for BridgePart, but you can not have choice (<|>) or failure (empty).

errorFixUp :: MonadReader BridgeData m => m PSType

A FixUpBridge which calles error when used. Usage:

buildBridgeWithCustomFixUp errorFixUp yourBridge

buildBridgeWithCustomFixUp :: FixUpBridge -> BridgePart -> FullBridge

Takes a constructed BridgePart and makes it a total function (FullBridge) by using the supplied FixUpBridge when BridgePart returns Nothing.