Does JSON allow positive sign for numbers?

Question

After examining the JSON.org railroad (grammar) definition, the number definition provides the negative sign (-), but omits recognizing the positive (+) sign - is this an omission from the diagram, or does JSON disallow postitive sign (+) for numbers?

The exponent allows optional positive (+) and negative (-) signs, so it would seem to save little to provide recognition of (+) for the number...

Answer 1

No, it doesn't.

Besides the grammar on json.org, JSON definitions are also provided by

• the ECMAScript Language definition, 5.1 Edition of June 2011
• RFC 7159 of March 2014

Concerning notation of signed numbers, they are all consistent. The former has

JSONNumber :: -? DecimalIntegerLiteral JSONFraction? ExponentPart?

while the latter says

number = [ minus ] int [ frac ] [ exp ]

Also all of these specifications allow an optional plus sign in the exponent, but none permits a plus sign to precede the numeric literal.