optional ( parser -- parser )

Vocabulary

peg

Inputs

parser

a parser

Outputs

parser

a parser

Word description

Returns a parser that parses 0 or 1 instances of the parser. The AST produced is f if 0 instances are parsed, otherwise it is the AST produced by parser.

Definition

USING: kernel peg.private ;

IN: peg

: optional ( parser -- parser ) optional-parser boa wrap-peg ;