proposal: Go 2: Allow question marks in function names

[sblackstone]

This comes from Ruby and its a real readability helper for functions that simply return booleans, e.g.

type OptionContract struct {
  Right string
}

func (oc *OptionContract) put?() bool {
  return oc.Right == 'P'
}

var (
  oc OptionContract
)

oc.right = 'P'

oc.put?() // True

[ALTree]

It's not much better than the "Is-" idiom - e.g. IsPrime - (in fact, personally I prefer the Is idiom over the ? idiom) and at the same time this would require complicating the rules for valid variable names (that right now are quite simple). Not sure it's worth it.

[ianlancetaylor]

If we adopt this, then why not ¿Poner? ? As @ALTree says, the current rules are simple.

[as]

The put? is very confusing, but isPut doesn't help either.

[sblackstone]

Regardless of whether you like the idiom or hate the idiom, whats so special about the question mark?

If...

func 世 int() {
	return 1
}

compiles because that character is part of UTF8, then why not the poor lowly ?

It's also a readability thing - when your eyes are scanning a line you get to find out whats being looked at before learning its a boolean.

e.g. (ruby)

if option.call? && option.long? // Do something particular.

[davecheney]

世 is defined as a letter by unicode ? is defined as a punctuation mark

…

On 2 July 2018 at 11:37, Stephen Blackstone ***@***.***> wrote: Regardless of whether you like the idiom or hate the idiom, whats so special about the question mark? If... func 世 int() { return 1 } compiles because that character is part of UTF8, why not the poor lowly ? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#26111 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAAcA6g4gz7y7AH4-anCpOs555gUdamuks5uCXlrgaJpZM4U70Gp> .

[sblackstone]

func helloɁ() {
	fmt.Println("Hello!")
}

Compiles... :-)

[davecheney]

Unicode says that's a letter, https://www.compart.com/en/unicode/U+0242

…

On 2 July 2018 at 11:53, Stephen Blackstone ***@***.***> wrote: func helloɁ() { fmt.Println("Hello!") } Compiles... — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#26111 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAAcAxX2NnttNPPmBfPwhEfhuo6m_C8bks5uCX0kgaJpZM4U70Gp> .

[sblackstone]

Why is "letterhood" or "punctuationhood" relevant?

The language doesn't include ternary expressions so its unlikely to be used in other contexts outside regex..

[Azareal]

If I recall, some of the ideas for generics or similar use question marks.
There were also some ideas for error handling which tossed question marks in.

Those might not make it into the language, but it's always good to keep the door open.
Plus, if question marks are valid, then I don't see why every other pieces of punctuation shouldn't be (not that it's practical to do so), otherwise you have to keep track of which ones are legal and which are not.

[davecheney]

Plus, if question marks are valid, then I don't see why every other pieces of punctuation shouldn't be (not that it's practical to do so), otherwise you have to keep track of which ones are legal and which are not.

x, y := package.a,b,c

what is x? It is the function package.a,b or is it the function package.a and y is the local variable b,c.

[ianlancetaylor]

@sblackstone Whether a character is a letter or punctuation is relevant because that is what the spec says today. From https://golang.org/ref/spec#Identifiers: "An identifier is a sequence of one or more letters and digits. The first character in an identifier must be a letter." Letter is defined at https://golang.org/ref/spec#Letters_and_digits as anything that Unicode considers to be a letter, plus the underscore character.