; metta.sgr -- MeTTa grammar in SGDL (Source Grammar Definition
;   Language) for the CCS toolchain. Compiling this grammar yields a
;   MeTTa frontend that turns .metta sources into CCS SCB binaries.
;   MeTTa needs three token classes beyond SGDL's predefined four --
;   see "MeTTa on CCS" section 1 -- so compile it with the MeTTa
;   tokenizer set (-lt). NOTE: this file uses ';' comments, not the
;   '--' of ALGOL-family grammars, because the tokenizer set that
;   reads it is MeTTa's.
; Source: hyperon-frontend-ccs metta.sgr @ 94f99e8 -- curated
;   2026-08-08; edits land in the source first.
; (c) 2026 BET THREE LLC. Published for use with the b3u.dev service
;   under its Terms of Service; all rights reserved.

(metta
  (program ::=
    0 = "  METAACTBEG();" =
    { sexpr }
    0 = "  METAACTEND();" =
  )

  (sexpr ::= atom | list )

  (list ::= '(' { sexpr } ')' )

  (atom ::= identifier
          | mettaSymbol
          | mettaVariable
          | mettaSpaceRef
          | stringToken
          | integerToken
          | equalTerm
          | colonTerm
          | lessThanTerm
          | greaterThanTerm
          | leftBracketTerm
          | rightBracketTerm
          | verticalBarTerm
          | leftBraceTerm
          | rightBraceTerm
          | dotTerm
          | commaTerm
          | slashTerm
          | edgeOpTerm
          | questionMarkTerm
          | apostropheTerm )

  (equalTerm         ::= '=' )
  (colonTerm         ::= ':' )
  (lessThanTerm      ::= '<' )
  (greaterThanTerm   ::= '>' )
  (leftBracketTerm   ::= '[' )
  (rightBracketTerm  ::= ']' )
  (verticalBarTerm   ::= '|' )
  (leftBraceTerm     ::= '{' )
  (rightBraceTerm    ::= '}' )
  (dotTerm           ::= '.' )
  (commaTerm         ::= ',' )
  (slashTerm         ::= '/' )
  (edgeOpTerm        ::= '->' )
  (questionMarkTerm  ::= '?' )
  (apostropheTerm    ::= '\'' )
)