Comment by Someone | Hacker News Reader

Comment by Someone | Hacker News Reader

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> Which makes sense, it's got the smallest language spec of any of them

I think go is fairly small, too, but “size of spec” is not always a good measure for that. Some specs are very tight, others fairly loose, and tightness makes specs larger (example: Swift’s language reference doesn’t even claim to define the full language. https://docs.swift.org/swift-book/documentation/the-swift-pr...: “The grammar described here is intended to help you understand the language in more detail, rather than to allow you to directly implement a parser or compiler.”)

(Also, browsing golang’s spec, I think I spotted an error in https://go.dev/ref/spec#Integer_literals. The grammar says:

  decimal_lit    = "0" | ( "1" … "9" ) [ [ "_" ] decimal_digits ] .

Given that, how can 0600 and 0_600 be valid integer literals in the examples?)

You're looking at the wrong production. They are octal literals:

    octal_lit      = "0" [ "o" | "O" ] [ "_" ] octal_digits .

Thanks! Never considered that a 21st century language designed for “power of two bits per word” hardware would keep that feature from the 1970s, so I never looked at that production.

Are there other modern languages that still have that?

0600 and 0_600 are octal literals:

    octal_lit      = "0" [ "o" | "O" ] [ "_" ] octal_digits .

Never mind, I was wrong. Here’s a playground showing how go parses each one: https://go.dev/play/p/hyWPkL_9C5W

> Octals must start with zero and then o/O literals.

No, the o/O is optional (hence in square brackets), only the leading zero is required. All of these are valid octal literals in Go:

0600 (zero six zero zero)

0_600 (zero underscore six zero zero)

0o600 (zero lower-case-letter-o six zero zero)

0O600 (zero upper-case-letter-o six zero zero)

My bad! I was wrong; added a playground demonstration the parsing behavior above.

My original comment was incorrect. These are being parsed as octals, not decimals: https://go.dev/play/p/hyWPkL_9C5W

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