[swift-evolution] Alternate proposal for multi-line string literial

[Patrick Gili]

https://doc.perl6.org/language/quoting

> On Mar 24, 2016, at 9:23 AM, Patrick Gili <gili.patrick.r at gili-labs.com> wrote:
> 
> I'm more in favor of Perl6 stye string literals, in general.
> 
> -Patrick
> 
>> On Mar 23, 2016, at 12:49 AM, Steve K. Chiu via swift-evolution <swift-evolution at swift.org> wrote:
>> 
>> Hi,
>> 
>> I am new to swift-evolution list, here is my draft proposal for the multi-line string literal problem.
>> The idea had been discussed in the list before, but it seems there are no real solution to many of the string literal problem.
>> Let's first define what are the problem with string literal:
>> 
>> 1. should be able to disable escape char
>> 
>> 2. or better, able to replace escape char with user defined char
>> 
>> 3. should be able to write multi-line string literal, and is copy-paste friendly
>> 
>> 4. for multi-line string, should be  able to remove first and last newline char, so user can write string in block
>> 
>> 5. for multi-line string, should be  able to remove leading indent, or remove all indent
>> 
>> 6. for multi-line string, should be  able to replace newline with user defined string ("\r\n", "\r", "\r", or simply " ")
>> 
>> 7. should be able to add feature over time, without breaking existing code
>> 
>> My proposal to the above problem is to introduce new 'process instruction' (not sure how to call it), in the following form:
>> 
>> #string(options) "text"
>> 
>> for example:
>> 
>> #string(escape: nil) "^\d+"
>> 
>> #string(escape: "$", end: "<EOF>") "
>>   $(username),
>>   Is it 1358 yet?
>> <EOF>"
>> 
>> It is possible to add many options list above, and you can add more options over time without breaking code.
>> 
>> #string(
>>    escape: Character? = "\\",    
>>    end: String? = nil,   
>>    skipEnclosureNewline: Bool = true,    
>>    skipLeadingIndent: Bool = true, 
>>    skipAllIndent: Bool = false,
>>    newline: String? = nil
>> )
>> 
>> for 1. & 2., escape option to replace escape char, pass nil will disable escape.
>> 
>> for 3., end option for end-of-string mark, pass nil will disable multi-line processing.
>> 
>> for 4., skipEnclosureNewline will skip newline if it is the first or last char of the string.
>> 
>> for 5., skipLeadingIndent will skip leading indent, leading indent is the leading white-spaces of first line of multi-line string.
>> 
>> for 5., skipAllIndent will skip all indent, this will override skipLeadingIndent.
>> 
>> for 6., newline option to replace newline char in multi-line string, pass nil will disable the replacement (as-is in the source).
>> 
>> But there are one problem remain, as you can see, the #string with options will become very long; I don't think it is a pleasure to use such expression except for one time literal. To fix the problem, I propose yet another process instruction:
>> 
>> #let #rex = #string(escape: nil)
>> #let #mail = #string(escape: "$", end: "<EOF>")
>> 
>> Now you can write the string as:
>> 
>> #rex "^\d+"
>> 
>> #mail "
>>   $(username),
>>   Is it 1358 yet?
>> <EOF>"
>> 
>> #let should be able to be used with other # process instruction as well, for example, #available, among other things.
>> 
>> What do you think?
>> 
>> 
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>