symantic/symantic.cabal

   1 author: Julien Moutinho <julm+symantic@autogeree.net>
   2 bug-reports: Julien Moutinho <julm+symantic@autogeree.net>
   3 build-type: Simple
   4 cabal-version: >= 1.24
   5 category: Language
   6 description:
   7  __Description__
   8  .
   9  Library for composing, typing, compiling, transforming and interpreting
  10  a custom DSL (Domain-Specific Language) expressing a subset of GHC's Haskell.
  11  Its main goal is to enable the runtime handling of terms typed
  12  according to some compile-time defined types.
  13  The idea being that the more complex logic shall remain coded in Haskell
  14  and then this library used to project an interface into a DSL
  15  giving runtime users the flexibility to write simpler programs suited to their needs.
  16  .
  17  Typical use cases:
  18  .
  19  * Enabling runtime users to enter some Haskell-like expressions
  20    without using all the weight and slowness of GHC
  21    at runtime (eg. by using <https://hackage.haskell.org/package/hint hint>).
  22  * Limiting those expressions to be built from well-controlled expressions only.
  23  * Run some analyzes/optimizations on those well-controlled expressions.
  24  .
  25  __Warning__
  26  .
  27  Please be aware that despite its using of powerful ideas from clever people,
  28  this remains a fund-less single-person experimental library.
  29  Meaning that it is all but heavily tested and documented,
  30  does not have a strong commitment to preserving backward compatibility,
  31  and can just die without notice (the Crohn infection I carry being only one of the many reasons).
  32  Its version follows the <http://www.haskell.org/haskellwiki/Package_versioning_policy PVP>,
  33  so you may want to use upper-bounds in @build-depends@.
  34  This said, I hope you'll enjoy the tool, or at least fish in it some inspiring ideas,
  35  'cause I had to smash those bytes with my poor head, day and night,
  36  a whole year of my life, to scult them as they currently are :P
  37  .
  38  __Usage__
  39  .
  40  Reading the boring @Test.hs@ files
  41  of <https://hackage.haskell.org/package/symantic-lib symantic-lib>
  42  should give you enough examples
  43  to understand how to use this library,
  44  and reading some of the repetitively boring
  45  and painfully repetitive @Lib/*.hs@ files
  46  of <https://hackage.haskell.org/package/symantic-lib symantic-lib>
  47  should give you some templates and the general pattern
  48  to let you extend this library with your own symantics.
  49  .
  50  The @Test.hs@ files use <https://hackage.haskell.org/package/megaparsec megaparsec> as parser
  51  and a default grammar somehow sticking to Haskell's, but staying context-free
  52  (so in particular: insensitive to the indentation).
  53  This grammar, itself written as a symantic embedded DSL,
  54  can be reused to build another one,
  55  is not bound to a specific parser,
  56  and can produce its EBNF rendition.
  57  .
  58  __Main ideas__
  59  .
  60  * __Symantic DSL__.
  61    To encode terms in the <http://okmij.org/ftp/tagless-final/ Tagless-Final> way
  62    (aka. the /symantic/ way)
  63    i.e. to use a /class/ to encode the /syntax/ of terms (eg. 'Sym_Bool')
  64    and /class instances/ on a dedicated type to encode their /semantics/
  65    (eg. @(Sym_Bool HostI)@ interprets a term as a value of its type
  66    in the host language (Haskell here),
  67    or @(Sym_Bool TextI)@ interprets a term as a textual rendition, etc.).
  68
  69    DSL are then composed by selecting those symantic /classes/.
  70    When using symantics for an embedded DSL
  71    those /classes/ are all inferred by GHC from the terms used,
  72    provided that the @NoMonomorphismRestriction@ extension is on.
  73    Otherwise, when using symantics for a non-embedded DSL
  74    — the whole point of this library — the /classes/ composing the DSL
  75    are selected manually at GHC's compile-time,
  76    through the /type-level list/ given to 'compile'.
  77
  78    Moreover, the terms are parameterized by the type of the value they encode,
  79    in order to get the same type safety as with plain Haskell values.
  80    Hence the symantic /classes/ have the higher kind: @((* -> *) -> Constraint)@
  81    instead of just @(* -> Constraint)@.
  82
  83    Amongst those symantics, 'Sym_Lambda' introduces /lambda abstractions/ by an higher-order approach,
  84    meaning that they directly reuse GHC's internal machinery
  85    to abstract or instantiate variables,
  86    which I think is by far the most efficient and simplest way of doing it
  87    (no DeBruijn encoding nor <https://hackage.haskell.org/package/bound bound>'s monads).
  88
  89  * __Singleton for any type__.
  90    To typecheck terms using a @(Type cs h)@ @GADT@ which acts
  91    as a /singleton type/ for any Haskell type @h@
  92    buildable by composing the /type constants/ @cs@,
  93    each one wrapped inside a @Proxy@ to fit into a common /type-level list/
  94    (eg. @cs ~ [Proxy Bool, Proxy (->), Proxy Eq]@).
  95
  96  * __Embed 'Term' in 'Type'__.
  97    To handle quantified (rank-1 only) and qualified terms,
  98    by using a rank-2 polymorphic function to introduce a bound type variable ('TyQuant'),
  99    and a function to pass the proof of a 'Constraint' ('TyQual').
 100    This is possible by loosing the type indexing of 'Type',
 101    because so far it is not possible to index quantified and qualified types
 102    (which would require a powerful /impredicative polymorphism/).
 103
 104  * __Extensible data type__.
 105    To inject a type into a /type-level list/
 106    or project a /type-level list/ onto a type,
 107    to compose an /extensible data type/
 108    (eg. the 'Token' @GADT@ gathering the 'TokenT' /data instances/,
 109    that a parser can build and then give to 'compile').
 110    This type-level programming requires @UndecidableInstances@,
 111    but not @OverlappingInstances@.
 112
 113    There is a similarity with
 114    <http://dx.doi.org/10.1017/S0956796808006758 Data types à la carte>
 115    (see for instance <https://hackage.haskell.org/package/compdata compdata>
 116    or <https://hackage.haskell.org/package/syntactic syntactic>).
 117    Those also enable to compose a DSL using some machinery
 118    based upon (co)free(r) (co)monads and (cata|ana)morphisms.
 119    Which library fits best your problem domain and brain is for you to judge :)
 120    On that topic, see also:
 121    <https://www.youtube.com/watch?v=qaAKRxO21fU Stop Paying for Free Monads>.
 122
 123    Here, I just came up using /type-level lists/ by hacking
 124    <https://hackage.haskell.org/package/glambda glambda>'s @Elem@.
 125
 126  * __Extensible class__.
 127    To recurse on a /type-level list/ through
 128    /class instances/ to compose an /extensible class/
 129    (eg. 'CompileR' gathering the 'CompileI' /class instances/,
 130    or the more tricky 'Term' /type-level list-zipper/
 131    gathering 'Sym_of_Iface' /class instances/
 132    while providing in scope the current 'Sym_of_Iface'
 133    within each 'Term' built in a 'CompileI' /class instance/).
 134  .
 135  __Main extensions__
 136  .
 137  * @GADTs@ for knowing types by pattern-matching terms,
 138    or building terms by using type classes.
 139  * @Rank2Types@ for parsing @GADT@s.
 140  * @TypeInType@ (introduced in GHC 8.0.1)
 141    for 'Type' to also bind a kind equality for the type @h@ it encodes.
 142    Which makes the /type application/ (':$')
 143    give us an /arrow kind/ for the Haskell /type constructor/
 144    it applies an Haskell type to, releaving me from tricky workarounds.
 145  * @ConstraintKinds@ for @cs@ to contain 'Constraint's,
 146    or defining /type synonym/ of /type classes/,
 147    or merging /type constraints/.
 148  * @DataKinds@ for type-level data structures (eg. /type-level lists/).
 149  * @TypeFamilies@ for type-level programming.
 150  * @UndecidableInstances@ for type-level programming
 151    that may never terminate.
 152  * @PolyKinds@ for avoiding a lot of uses of 'Proxy'.
 153  * @TypeApplications@ for having a more concise syntax
 154    to build 'Type' (eg. @ty \@Bool@).
 155  * @DefaultSignatures@ for providing identity transformations of terms,
 156    and thus avoid boilerplate code when a transformation
 157    does not need to alter all semantics.
 158    As explained in <https://ro-che.info/articles/2016-02-03-finally-tagless-boilerplate Reducing boilerplate in finally tagless style>.
 159  .
 160  __Bugs__
 161  .
 162  There are some of them hidding in there,
 163  and the whole thing is far from being perfect!
 164  Whatever your comments, problem reports, or questions, they are welcome!
 165  You have my email address, so… just send me some emails :]
 166  .
 167  __To do__
 168  .
 169  * Study to which point /type inferencing/ is doable,
 170    now that 'Type' is powerful enough to handle 'TyVar's.
 171  * Study to which point error messages can be improved,
 172    now that there is a 'Source' carried through all 'Kind's or 'Type's,
 173    it should enable some nice reports.
 174  * A lot of common terms should be added in @Lib.*@ modules.
 175  * No transformation is implemented so far,
 176    maybe there should be some, at least as examples
 177    to demonstrate their power.
 178  * Study where to put @INLINE@, @INLINEABLE@ or @SPECIALIZE@ pragmas.
 179 extra-source-files:
 180 extra-tmp-files:
 181 -- homepage:
 182 license: GPL-3
 183 license-file: COPYING
 184 maintainer: Julien Moutinho <julm+symantic@autogeree.net>
 185 name: symantic
 186 stability: experimental
 187 synopsis: Library for Typed Tagless-Final Higher-Order Composable DSL
 188 tested-with: GHC==8.0.2
 189 -- PVP:  +-+------- breaking API changes
 190 --       | | +----- non-breaking API additions
 191 --       | | | +--- code changes with no API change
 192 version: 5.0.0.20170430
 193
 194 Source-Repository head
 195   location: git://git.autogeree.net/symantic
 196   type:     git
 197
 198 Library
 199   default-extensions:
 200     DataKinds
 201     DefaultSignatures
 202     FlexibleContexts
 203     FlexibleInstances
 204     InstanceSigs
 205     LambdaCase
 206     MultiParamTypeClasses
 207     NamedFieldPuns
 208     OverloadedStrings
 209     Rank2Types
 210     ScopedTypeVariables
 211     StandaloneDeriving
 212     TupleSections
 213     TypeApplications
 214     TypeFamilies
 215     TypeOperators
 216   ghc-options: -Wall
 217                -fwarn-incomplete-patterns
 218                -fno-warn-tabs
 219                -fprint-explicit-kinds
 220   default-language: Haskell2010
 221   exposed-modules:
 222     Language.Symantic
 223     -- Language.Symantic.Compiling
 224     -- Language.Symantic.Compiling.Term
 225     -- Language.Symantic.Compiling.Term.Grammar
 226     Language.Symantic.Helper.Data.Type.List
 227     Language.Symantic.Helper.Data.Type.Peano
 228     Language.Symantic.Interpreting
 229     Language.Symantic.Interpreting.Dup
 230     Language.Symantic.Interpreting.Host
 231     Language.Symantic.Interpreting.Text
 232     Language.Symantic.Parsing
 233     Language.Symantic.Parsing.Token
 234     Language.Symantic.Transforming
 235     Language.Symantic.Transforming.Trans
 236     Language.Symantic.Typing
 237     Language.Symantic.Typing.Constant
 238     Language.Symantic.Typing.Constraint
 239     Language.Symantic.Typing.Family
 240     Language.Symantic.Typing.Kind
 241     Language.Symantic.Typing.Type
 242   build-depends:
 243     base >= 4.6 && < 5
 244     , containers
 245     , ghc-prim
 246     , mono-traversable
 247     , symantic-grammar
 248     , transformers
 249     , text