A JSON array is an ordered value containing comma-separated JSON values inside square brackets. Its elements may be literals, objects, or nested arrays. section 9.4.1
A parser for JSON arrays makes the structure explicit:
- Consumes an opening square bracket, parses a value, and repeats separator–value pairs. section 9.8
- Allows an empty array by choosing between one-or-more separated values and an empty result. section 9.8
- Discards commas and converts the parsed list into an IndexedSeq stored by JArray. section 9.8
- Handles surrounding whitespace with token parsers and adds array context to parse failures. section 9.8
A nested array value
The Related companies field contains ["HPQ", "IBM", "YHOO", "DELL", "GOOG"]. A parser represents these ordered strings as a JArray, while the surrounding document remains a JObject. section 9.4.1
def token(s: String): Parser[String] =
string(s).attempt <* whitespace
def array: Parser[JSON] =
token("[") *> value.sep(token(",")).map(vs =>
JArray(vs.toIndexedSeq)) <* token("]")
This implementation shows the array grammar after whitespace has been incorporated: tokens surround the brackets and commas, while value.sep collects the elements. section 9.8
