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

[Patrick Gili]

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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