   { "quot" quotation }
   { "parser" parser }
 }
-{ $description 
+{ $description
     "Returns a parser that calls the quotation on the first character of the input string, "
     "succeeding if that quotation returns true. The AST is the character from the string." } ;
 

  { "seq" "a sequence of parsers" }
  { "parser" parser }
}
{ $description 
    "Returns a parser that calls all parsers in the given sequence, in order. The parser succeeds if "
    "all the parsers succeed, otherwise it fails. The AST produced is a sequence of the AST produced by "
    "the individual parsers." } ;

HELP: choice
{ $values 
  { "seq" "a sequence of parsers" } 
  { "parser" parser } 
}
{ $description 
    "Returns a parser that will try all the parsers in the sequence, in order, until one succeeds. "
    "The resulting AST is that produced by the successful parser." } ;

HELP: repeat0
{ $values 
  { "parser" parser } 
}
{ $description 
    "Returns a parser that parses 0 or more instances of the 'p1' parser. The AST produced is "
    "an array of the AST produced by the 'p1' parser. An empty array indicates 0 instances were "
    "parsed." } ;

HELP: repeat1
{ $values 
  { "parser" parser } 
}
{ $description 
    "Returns a parser that parses 1 or more instances of the 'p1' parser. The AST produced is "
    "an array of the AST produced by the 'p1' parser." } ;

HELP: optional
{ $values 
  { "parser" parser } 
}
{ $description 
    "Returns a parser that parses 0 or 1 instances of the 'p1' parser. The AST produced is "
    "'f' if 0 instances are parsed the AST produced is 'f', otherwise it is the AST produced by 'p1'." } ;

HELP: semantic
{ $values 
  { "parser" parser } 
  { "quot" { $quotation ( object -- ? ) } } 
}
{ $description 
    "Returns a parser that succeeds if the 'p1' parser succeeds and the quotation called with "
    "the AST produced by 'p1' on the stack returns true." }
{ $examples 
  { $example "USING: kernel math peg prettyprint ;" "\"C\" [ drop t ] satisfy [ 66 > ] semantic parse ." "67" } 
} ;

HELP: ensure
{ $values 
  { "parser" parser } 
}
{ $description 
    "Returns a parser that succeeds if the 'p1' parser succeeds but does not add anything to the "
    "AST and does not move the location in the input string. This can be used for lookahead and "
    "disambiguation, along with the " { $link ensure-not } " word." }
{ $examples { $code "\"0\" token ensure octal-parser" } } ;

HELP: ensure-not
{ $values 
  { "parser" parser } 
}
{ $description 
    "Returns a parser that succeeds if the 'p1' parser fails but does not add anything to the "
    "AST and does not move the location in the input string. This can be used for lookahead and "
    "disambiguation, along with the " { $link ensure } " word." }
{ $code "\"+\" token \"=\" token ensure-not \"+=\" token 3array seq" } ;

HELP: action
{ $values 
  { "parser" parser } 
  { "quot" { $quotation ( ast -- ast ) } } 
}
{ $description 
    "Returns a parser that calls the 'p1' parser and applies the quotation to the AST resulting "
    "from that parse. The result of the quotation is then used as the final AST. This can be used "
    "for manipulating the parse tree to produce a AST better suited for the task at hand rather than "

{ $code "CHAR: 0 CHAR: 9 range [ to-digit ] action" } ;

HELP: sp
{ $values
  { "parser" parser }
}
{ $description
    "Returns a parser that calls the original parser 'p1' after stripping any whitespace "
    " from the left of the input string." } ;

HELP: hide
{ $values
  { "parser" parser }
}
{ $description
    "Returns a parser that succeeds if the original parser succeeds, but does not "
    "put any result in the AST. Useful for ignoring 'syntax' in the AST." }
{ $code "\"[\" token hide number \"]\" token hide 3array seq" } ;

HELP: delay
{ $values
  { "quot" quotation }
  { "parser" parser }
}
{ $description
    "Delays the construction of a parser until it is actually required to parse. This "
    "allows for calling a parser that results in a recursive call to itself. The quotation "
    "should return the constructed parser and is called the first time the parser is run. "
    "The compiled result is memoized for future runs. See " { $link box } " for a word "
    "that calls the quotation at compile time." } ;

HELP: box
{ $values
  { "quot" quotation }
  { "parser" parser }
}
{ $description
    "Delays the construction of a parser until the parser is compiled. The quotation "
    "should return the constructed parser and is called when the parser is compiled. "
    "The compiled result is memoized for future runs. See " { $link delay } " for a word "
    "that calls the quotation at runtime." } ;
