REQUIRES: contrib/lazy-lists contrib/parser-combinators ;

USING: kernel math strings sequences lazy-lists parser-combinators ;

IN: sexp

LAZY: 'lparens' ( -- parser )
  "(" token ;

LAZY: 'rparens' ( -- parser )
  ")" token ;

LAZY: 'identifier' ( -- parser )
  [
    [ blank? not ] keep
    [ digit? not ] keep
    [ CHAR: ( = not ] keep
    CHAR: ) = not
    and and and    
  ] satisfy <+> [ >string ] <@ ;

LAZY: 'digit' ( -- parser )
  [ digit? ] satisfy [ digit> ] <@ ;

LAZY: 'number' ( -- parser )
  'digit' <+> [ 0 [ swap 10 * + ] reduce ] <@ ;

LAZY: 'atom' ( -- parser )
  'identifier' 'number' <|> ;

LAZY: 'expr' ( -- parser )
  'atom'   
  'lparens'
  'atom' 'expr' <|> sp <*> &>
  'rparens' <& [ >quotation ] <@ <|> ;

: reader ( input -- value )
  'expr' just some parse force ;

: test1 ( -- value )
  "(+ dfg 20 30)" 'expr' just some parse force ;