preserves/schema/schema.prs

@<EmacsMode "-*- preserves -*-">

version 1 .

Schema = <schema {
  version: Version
  pointer: PointerName
  definitions: Definitions
}>.

; version 1 .
Version = 1 .

PointerName = Ref / #f.

Definitions = { symbol: Definition ...:... }.

; Pattern / Pattern / ...
; and the empty pattern is <or []>
Definition = <or [@patterns NamedAlternative ...]> / Alternative .

NamedAlternative = [@variantLabel string @alternative Alternative].

; Pattern & Pattern & ...
; and the universal pattern, "any", is <and []>
Alternative = <and [@patterns NamedPattern ...]> / Pattern .

Pattern = SimplePattern / CompoundPattern .

SimplePattern =
  ; special builtins
  / <atom @atomKind AtomKind>

  ; matches a pointer in the input
  / <pointer>

  ; =symbol, <<lit> any>, or plain non-symbol atom
  / <lit @value any>

  ; symbol, symbol.symbol, symbol.symbol.symbol, ...
  / Ref
.

CompoundPattern =
  ; <label a b c> ----> <rec <lit label> <tuple [<ref a> <ref b> <ref c>]>>
  ; except for record labels
  ; <<rec> x y> ---> <rec <ref x> <ref y>>
  / <rec @label NamedPattern @fields NamedPattern>

  ; [a b c] ----> <tuple [<ref a> <ref b> <ref c>]>
  / <tuple [@patterns NamedPattern ...]>

  ; [a b c ...] ----> <tuple* [<ref a> <ref b>] <ref c>]>
  / <tuple* [@fixed NamedPattern ...] @variable NamedSimplePattern>

  ; #{p} ----> <setof <ref p>>
  / <setof @pattern SimplePattern>

  ; {k: v, ...:...} ----> <dictof <ref k> <ref v>>
  / <dictof @key SimplePattern @value SimplePattern>

  ; {a: b, c: d} ----> <dict {a: <ref b>, c: <ref d>}>
  / <dict @entries DictionaryEntries>
.

DictionaryEntries = { any: NamedSimplePattern ...:... }.

AtomKind = =Boolean / =Float / =Double / =SignedInteger / =String / =ByteString / =Symbol .

NamedSimplePattern = @named NamedSimplePattern_ / @anonymous SimplePattern .
NamedPattern = @named NamedSimplePattern_ / @anonymous Pattern .

NamedSimplePattern_ = <named @name symbol @pattern SimplePattern>.

Ref = <ref @module ModulePath @name symbol>.
ModulePath = [symbol ...].