cabal-version: 1.18 name: Rattus version: 0.2 category: FRP synopsis: A modal FRP language description: This library implements the Rattus programming language as an embedded DSL. To this end the library provides a GHC plugin that performs the additional checks that are necessary for Rattus. What follows is a brief introduction to the language and its usage. A more detailed introduction can be found in this . . Rattus is a functional reactive programming (FRP) language that uses modal types to ensure operational properties that are crucial for reactive programs: productivity (in each computation step, the program makes progress), causality (output depends only on current and earlier input), and no implicit space leaks (programs do not implicitly retain memory over time). . To ensure these properties, Rattus uses the type modality @O@ to express the concept of time at the type level. Intuitively speaking, a value of type @O a@ represents a computation that will produce a value of type @a@ in the next time step. Additionally, the language also features the @Box@ type modality. A value of type @Box a@ is a time-independent computation that can be executed at any time to produce a value of type @a@. . For example, the type of streams is defined as . > data Str a = a ::: (O (Str a)) . So the head of the stream is available now, but its tail is only available in the next time step. Writing a @map@ function for this type of streams, requires us to use the @Box@ modality: . > map :: Box (a -> b) -> Str a -> Str b > map f (x ::: xs) = unbox f x ::: delay (map f (adv xs)) . This makes sure that the function @f@ that we give to @map@ is available at any time in the future. . The core of the language is defined in the module "Rattus.Primitives". Note that the operations on @O@ and @Box@ have non-standard typing rules. Therefore, this library provides a compiler plugin that checks these non-standard typing rules. To write Rattus programs, one must enable this plugin via the GHC option @-fplugin=Rattus.Plugin@, e.g. by including the following line in the source file (for better error messages we also suggest using the option @-g2@): . > {-# OPTIONS -fplugin=Rattus.Plugin #-} . In addition, one must annotate the functions that are written in Rattus: . > {-# ANN myFunction Rattus #-} . Or annotate the whole module as a Rattus module: . > {-# ANN module Rattus #-} . Below is a minimal Rattus program using the "Rattus.Stream" module for programming with streams: . > {-# OPTIONS -fplugin=Rattus.Plugin #-} > > import Rattus > import Rattus.Stream > > {-# ANN sums Rattus #-} > sums :: Str Int -> Str Int > sums = scan (box (+)) 0 . The provides more examples on how to program in Rattus. homepage: https://github.com/pa-ba/Rattus bug-reports: https://github.com/pa-ba/Rattus/issues License: BSD3 License-file: LICENSE copyright: Copyright (C) 2020 Patrick Bahr Author: Patrick Bahr maintainer: Patrick Bahr stability: experimental build-type: Custom extra-source-files: CHANGELOG.md extra-doc-files: docs/paper.pdf custom-setup setup-depends: base >= 4.5 && < 5, Cabal >= 1.18 library exposed-modules: Rattus Rattus.Stream Rattus.Strict Rattus.Event Rattus.Events Rattus.ToHaskell Rattus.Yampa Rattus.Plugin Rattus.Arrow Rattus.Primitives other-modules: Rattus.Plugin.ScopeCheck Rattus.Plugin.Strictify Rattus.Plugin.Utils Rattus.Plugin.StableSolver build-depends: base >=4.12 && <5, containers, simple-affine-space, ghc >= 8.6 hs-source-dirs: src default-language: Haskell2010 ghc-options: -W -g2 Test-Suite memory-leak type: exitcode-stdio-1.0 main-is: MemoryLeak.hs hs-source-dirs: test default-language: Haskell2010 build-depends: Rattus, base ghc-options: -fplugin=Rattus.Plugin -rtsopts -g2 Test-Suite time-leak type: exitcode-stdio-1.0 main-is: TimeLeak.hs hs-source-dirs: test default-language: Haskell2010 build-depends: Rattus, base ghc-options: -fplugin=Rattus.Plugin -rtsopts -g2 Test-Suite ill-typed type: exitcode-stdio-1.0 main-is: test/IllTyped.hs default-language: Haskell2010 build-depends: Rattus, base ghc-options: -fplugin=Rattus.Plugin -rtsopts -g2 Test-Suite well-typed type: exitcode-stdio-1.0 main-is: WellTyped.hs hs-source-dirs: test default-language: Haskell2010 build-depends: Rattus, base, containers ghc-options: -fplugin=Rattus.Plugin -rtsopts -g2 Test-Suite rewrite type: exitcode-stdio-1.0 main-is: Rewrite.hs hs-source-dirs: test default-language: Haskell2010 build-depends: Rattus, base, containers ghc-options: -fplugin=Rattus.Plugin -rtsopts -g2