name:                ghc-typelits-knownnat
version:             0.1.1
synopsis:            Derive KnownNat constraints from other KnownNat constraints
description:
  A type checker plugin for GHC that can derive \"complex\" @KnownNat@
  constraints from other simple/variable @KnownNat@ constraints. i.e. without
  this plugin, you must have both a @KnownNat n@ and a @KnownNat (n+2)@
  constraint in the type signature of the following function:
  .
  @
  f :: forall n . (KnownNat n, KnownNat (n+2)) => Proxy n -> Integer
  f _ = natVal (Proxy :: Proxy n) + natVal (Proxy :: Proxy (n+2))
  @
  .
  Using the plugin you can omit the @KnownNat (n+2)@ constraint:
  .
  @
  f :: forall n . KnownNat n => Proxy n -> Integer
  f _ = natVal (Proxy :: Proxy n) + natVal (Proxy :: Proxy (n+2))
  @
  .
  The plugin can only derive @KnownNat@ constraints consisting of:
  .
  * Type-level naturals
  .
  * Type variables
  .
  * Applications of the arithmetic expression: +,*,^
  .
  i.e. it /cannot/ derive a @KnownNat (n-1)@ constraint from a @KnownNat n@
  constraint
  .
  To use the plugin, add the
  .
  @
  OPTIONS_GHC -fplugin GHC.TypeLits.KnownNat.Solver
  @
  .
  Pragma to the header of your file.
homepage:            http://clash-lang.org/
license:             BSD2
license-file:        LICENSE
author:              Christiaan Baaij
maintainer:          christiaan.baaij@gmail.com
copyright:           Copyright © 2016 University of Twente
category:            Type System
build-type:          Simple
extra-source-files:  README.md
                     CHANGELOG.md
cabal-version:       >=1.10

source-repository head
  type: git
  location: https://github.com/clash-lang/ghc-typelits-knownnat.git

flag deverror
  description:
    Enables `-Werror` for development mode and TravisCI
  default: False
  manual: True

library
  exposed-modules:     GHC.TypeLits.KnownNat.Solver,
                       GHC.TypeLits.KnownNat
  other-extensions:    AllowAmbiguousTypes
                       DataKinds
                       FlexibleInstances
                       MultiParamTypeClasses
                       KindSignatures
                       ScopedTypeVariables
                       TupleSections
                       TypeApplications
                       TypeOperators
  build-depends:       base                >= 4.9   && <4.10,
                       ghc                 >= 8.0.1 && <8.2,
                       ghc-tcplugins-extra >= 0.2
  hs-source-dirs:      src
  default-language:    Haskell2010
  if flag(deverror)
    ghc-options:       -Wall -Werror
  else
    ghc-options:       -Wall

test-suite test-ghc-typelits-knownat
  type:                exitcode-stdio-1.0
  main-is:             Main.hs
  build-depends:       base                      >= 4.8 && <5,
                       ghc-typelits-knownnat     >= 0.1,
                       tasty                     >= 0.10,
                       tasty-hunit               >= 0.9
  hs-source-dirs:      tests
  default-language:    Haskell2010
  other-extensions:    DataKinds
                       ScopedTypeVariables
                       TypeApplications
                       TypeOperators
  if flag(deverror)
    ghc-options:       -O0 -dcore-lint