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(.module:
lux
(lux (control [monad #+ do Monad]
["p" parser])
(data [text "text/" Eq<Text> Monoid<Text>]
["E" error]
(coll [list "list/" Functor<List> Monoid<List>]))
[macro]
(macro [code]
["s" syntax #+ syntax:]
(syntax ["cs" common]
(common ["csr" reader]
["csw" writer])))))
(def: (get k plist)
(All [a]
(-> Text (List [Text a]) (Maybe a)))
(case plist
#.Nil
#.None
(#.Cons [k' v] plist')
(if (text/= k k')
(#.Some v)
(get k plist'))))
(def: (put k v plist)
(All [a]
(-> Text a (List [Text a]) (List [Text a])))
(case plist
#.Nil
(list [k v])
(#.Cons [k' v'] plist')
(if (text/= k k')
(#.Cons [k' v] plist')
(#.Cons [k' v'] (put k v plist')))))
(def: (remove k plist)
(All [a]
(-> Text (List [Text a]) (List [Text a])))
(case plist
#.Nil
#.Nil
(#.Cons [k' v'] plist')
(if (text/= k k')
plist'
(#.Cons [k' v'] (remove k plist')))))
(def: down-cast Text ":abstraction")
(def: up-cast Text ":representation")
(def: macro-anns Code (' {#.macro? true}))
(def: representation-name
(-> Text Text)
(|>> ($_ text/compose "{" kind "@" module "}")
(let [[module kind] (ident-for #..Representation)])))
(def: (install-casts' this-module-name name type-vars)
(-> Text Text (List Text) (Meta Any))
(do macro.Monad<Meta>
[this-module (macro.find-module this-module-name)
#let [type-varsC (list/map code.local-symbol type-vars)
abstract-declaration (` ((~ (code.local-symbol name)) (~+ type-varsC)))
representation-declaration (` ((~ (code.local-symbol (representation-name name))) (~+ type-varsC)))
this-module (|> this-module
(update@ #.definitions (put down-cast (: Definition
[Macro macro-anns
(: Macro
(function (_ tokens)
(case tokens
(^ (list value))
(wrap (list (` ((: (All [(~+ type-varsC)]
(-> (~ representation-declaration) (~ abstract-declaration)))
(|>> :assume))
(~ value)))))
_
(macro.fail ($_ text/compose "Wrong syntax for " down-cast)))))])))
(update@ #.definitions (put up-cast (: Definition
[Macro macro-anns
(: Macro
(function (_ tokens)
(case tokens
(^ (list value))
(wrap (list (` ((: (All [(~+ type-varsC)]
(-> (~ abstract-declaration) (~ representation-declaration)))
(|>> :assume))
(~ value)))))
_
(macro.fail ($_ text/compose "Wrong syntax for " up-cast)))))]))))]]
(function (_ compiler)
(#E.Success [(update@ #.modules (put this-module-name this-module) compiler)
[]]))))
(def: (un-install-casts' this-module-name)
(-> Text (Meta Any))
(do macro.Monad<Meta>
[this-module (macro.find-module this-module-name)
#let [this-module (|> this-module
(update@ #.definitions (remove down-cast))
(update@ #.definitions (remove up-cast)))]]
(function (_ compiler)
(#E.Success [(update@ #.modules (put this-module-name this-module) compiler)
[]]))))
(syntax: (install-casts {name s.local-symbol}
{type-vars (s.tuple (p.some s.local-symbol))})
(do @
[this-module-name macro.current-module-name
?down-cast (macro.find-macro [this-module-name down-cast])
?up-cast (macro.find-macro [this-module-name up-cast])]
(case [?down-cast ?up-cast]
[#.None #.None]
(do @
[_ (install-casts' this-module-name name type-vars)]
(wrap (list)))
_
(macro.fail ($_ text/compose
"Cannot temporarily define casting functions ("
down-cast " & " up-cast
") because definitions like that already exist.")))))
(syntax: (un-install-casts)
(do macro.Monad<Meta>
[this-module-name macro.current-module-name
?down-cast (macro.find-macro [this-module-name down-cast])
?up-cast (macro.find-macro [this-module-name up-cast])]
(case [?down-cast ?up-cast]
[(#.Some _) (#.Some _)]
(do @
[_ (un-install-casts' this-module-name)]
(wrap (list)))
_
(macro.fail ($_ text/compose
"Cannot un-define casting functions ("
down-cast " & " up-cast
") because they do not exist.")))))
(def: declaration
(s.Syntax [Text (List Text)])
(p.either (s.form (p.seq s.local-symbol (p.some s.local-symbol)))
(p.seq s.local-symbol (:: p.Monad<Parser> wrap (list)))))
(syntax: #export (abstract:
{export csr.export}
{[name type-vars] declaration}
{annotations (p.default cs.empty-annotations csr.annotations)}
representation-type
{primitives (p.some s.any)})
(let [hidden-name (representation-name name)
type-varsC (list/map code.local-symbol type-vars)
abstract-declaration (` ((~ (code.local-symbol name)) (~+ type-varsC)))
representation-declaration (` ((~ (code.local-symbol hidden-name)) (~+ type-varsC)))]
(wrap (list& (` (type: (~+ (csw.export export)) (~ abstract-declaration)
(~ (csw.annotations annotations))
(primitive (~ (code.text hidden-name)) [(~+ type-varsC)])))
(` (type: (~+ (csw.export export)) (~ representation-declaration)
(~ representation-type)))
(` ((~! install-casts) (~ (code.local-symbol name)) [(~+ type-varsC)]))
(list/compose primitives
(list (` ((~! un-install-casts)))))))))
(syntax: #export (^:representation {name (s.form s.local-symbol)}
body
{branches (p.some s.any)})
(let [g!representation (code.local-symbol name)]
(do @
[current-module macro.current-module-name
#let [g!:representation (code.symbol [current-module up-cast])]]
(wrap (list& g!representation
(` (.let [(~ g!representation) ((~ g!:representation) (~ g!representation))]
(~ body)))
branches)))))
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