SE-0168: Multi-Line String Literals


(Dave Yost) #1

Beauty is a top-three goal of Swift, so a proposal that is not beautiful should be rethought until it is.

1. """ is ugly.

2. Choosing syntax so as to pander to hacks in a few existing tools is the road to Ugly.

3. It’s inelegant syntax design for start and end delimiters to be identical, as for example ASCII quote marks are.[1]

4. Mirror image start and end delimiters are preferred, for example { and }.[1]

5. Escaping is ugly and preferably should not be necessary or even allowed.

Therefore, I propose, by example:

  let foo =
    /"xx
    The indent of /"
        dictates indentation and must match
    all indents through the "/
    "/xx

where an optional arbitrary identifier, for example “xx”, can be appended to both the open and the close quote delimiters to avoid the need for escaping the close quote delimiter. The identifier has no other significance in the program.

I further propose that /' and '/ should be used to delimit a string that is interpreted literally, including newlines except for the newline on the last line of the string.

In future, consideration should be given to the idea of following the /" delimiter by a set of space-separated flags to determine treatment of newlines, the escape character (so it doesn’t have to be backslash), use of interpolated strings, the use of escape characters, etc.

Dave

(I intended all single and double quotes in this message to be ASCII, not curly. If any are curly, then blame the macOS Mail app.)

[1]. I think Swift should allow delimiting strings with “curly” quotes, and they should nest. See 3, 4, 5 above.


(Beta) #2

A quick question since we’ve already accepted this proposal and have an implementation in-tree: do you expect this breaking change to be accepted for Swift 4, or do you expect this change to break everybody once they’ve already migrated to the triple-quoted string form in a future release?

~Robert Widmann

···

On May 25, 2017, at 11:02 PM, Dave Yost via swift-evolution <swift-evolution@swift.org> wrote:

Beauty is a top-three goal of Swift, so a proposal that is not beautiful should be rethought until it is.

1. """ is ugly.

2. Choosing syntax so as to pander to hacks in a few existing tools is the road to Ugly.

3. It’s inelegant syntax design for start and end delimiters to be identical, as for example ASCII quote marks are.[1]

4. Mirror image start and end delimiters are preferred, for example { and }.[1]

5. Escaping is ugly and preferably should not be necessary or even allowed.

Therefore, I propose, by example:

  let foo =
    /"xx
    The indent of /"
        dictates indentation and must match
    all indents through the "/
    "/xx

where an optional arbitrary identifier, for example “xx”, can be appended to both the open and the close quote delimiters to avoid the need for escaping the close quote delimiter. The identifier has no other significance in the program.

I further propose that /' and '/ should be used to delimit a string that is interpreted literally, including newlines except for the newline on the last line of the string.

In future, consideration should be given to the idea of following the /" delimiter by a set of space-separated flags to determine treatment of newlines, the escape character (so it doesn’t have to be backslash), use of interpolated strings, the use of escape characters, etc.

Dave

(I intended all single and double quotes in this message to be ASCII, not curly. If any are curly, then blame the macOS Mail app.)

[1]. I think Swift should allow delimiting strings with “curly” quotes, and they should nest. See 3, 4, 5 above.

_______________________________________________
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https://lists.swift.org/mailman/listinfo/swift-evolution


(Adrian Zubarev) #3

Well /" "/ is far from being the queen of the beautiful syntaxes.

I summed up my thoughts in the following two gists:

https://gist.github.com/DevAndArtist/d9282e032ee241cfd1a403961cedffdf
https://gist.github.com/DevAndArtist/0c95f8549bb7d97387b360b4cfb3e09e
David Hart and I are patiently waiting for post WWDC to see how the broader mass will react to the accepted changes. Furthermore, Chris Lattner said that he views WWDC betas as the way to figure out if proposals need to be fixed before release.

···

--
Adrian Zubarev
Sent with Airmail

Am 26. Mai 2017 um 08:02:28, Dave Yost via swift-evolution (swift-evolution@swift.org) schrieb:

Beauty is a top-three goal of Swift, so a proposal that is not beautiful should be rethought until it is.

1. """ is ugly.

2. Choosing syntax so as to pander to hacks in a few existing tools is the road to Ugly.

3. It’s inelegant syntax design for start and end delimiters to be identical, as for example ASCII quote marks are.[1]

4. Mirror image start and end delimiters are preferred, for example { and }.[1]

5. Escaping is ugly and preferably should not be necessary or even allowed.

Therefore, I propose, by example:

let foo =
/"xx
The indent of /"
dictates indentation and must match
all indents through the "/
"/xx

where an optional arbitrary identifier, for example “xx”, can be appended to both the open and the close quote delimiters to avoid the need for escaping the close quote delimiter. The identifier has no other significance in the program.

I further propose that /' and '/ should be used to delimit a string that is interpreted literally, including newlines except for the newline on the last line of the string.

In future, consideration should be given to the idea of following the /" delimiter by a set of space-separated flags to determine treatment of newlines, the escape character (so it doesn’t have to be backslash), use of interpolated strings, the use of escape characters, etc.

Dave

(I intended all single and double quotes in this message to be ASCII, not curly. If any are curly, then blame the macOS Mail app.)

[1]. I think Swift should allow delimiting strings with “curly” quotes, and they should nest. See 3, 4, 5 above.

_______________________________________________
swift-evolution mailing list
swift-evolution@swift.org
https://lists.swift.org/mailman/listinfo/swift-evolution


(Dave Yost) #4

I regret that I didn't send my two proposals much earlier, but I was operating under the assumption that Swift 4 was not going to include changes such as this, so I thought I should wait and was surprised to stumble on this change. (I wonder if anyone else is in the same boat.)

If people are not sure the existing commit is optimal, certainly it would make sense for it to be backed out sooner rather than later.

Btw I don't mean for the close quote delimiter to be the only thing on the line, as one might expect by analogy with shell syntax.

Dave

···

On May 25, 2017, at 11:24 PM, Robert Widmann <rwidmann@apple.com> wrote:

A quick question since we’ve already accepted this proposal and have an implementation in-tree: do you expect this breaking change to be accepted for Swift 4, or do you expect this change to break everybody once they’ve already migrated to the triple-quoted string form in a future release?

~Robert Widmann

On May 25, 2017, at 11:02 PM, Dave Yost via swift-evolution <swift-evolution@swift.org> wrote:

Beauty is a top-three goal of Swift, so a proposal that is not beautiful should be rethought until it is.

1. """ is ugly.

2. Choosing syntax so as to pander to hacks in a few existing tools is the road to Ugly.

3. It’s inelegant syntax design for start and end delimiters to be identical, as for example ASCII quote marks are.[1]

4. Mirror image start and end delimiters are preferred, for example { and }.[1]

5. Escaping is ugly and preferably should not be necessary or even allowed.

Therefore, I propose, by example:

  let foo =
    /"xx
    The indent of /"
        dictates indentation and must match
    all indents through the "/
    "/xx

where an optional arbitrary identifier, for example “xx”, can be appended to both the open and the close quote delimiters to avoid the need for escaping the close quote delimiter. The identifier has no other significance in the program.

I further propose that /' and '/ should be used to delimit a string that is interpreted literally, including newlines except for the newline on the last line of the string.

In future, consideration should be given to the idea of following the /" delimiter by a set of space-separated flags to determine treatment of newlines, the escape character (so it doesn’t have to be backslash), use of interpolated strings, the use of escape characters, etc.

Dave

(I intended all single and double quotes in this message to be ASCII, not curly. If any are curly, then blame the macOS Mail app.)

[1]. I think Swift should allow delimiting strings with “curly” quotes, and they should nest. See 3, 4, 5 above.

_______________________________________________
swift-evolution mailing list
swift-evolution@swift.org
https://lists.swift.org/mailman/listinfo/swift-evolution


(Dave Yost) #5

Sorry, to be clearer the close quote delimiter must be the first thing on the line following indenting whitespace, but it need not be the last thing on the line.

···

On May 26, 2017, at 9:47 AM, Dave Yost <Dave@Yost.com> wrote:

Btw I don't mean for the close quote delimiter to be the only thing on the line, as one might expect by analogy with shell syntax.