Fwd: String reboot proposal

[Brian Goetz]

Received on the -comments list.

> Begin forwarded message:
> 
> From: Victor Nazarov <asviraspossible at gmail.com>
> Subject: String reboot proposal
> Date: April 16, 2019 at 10:19:06 PM EDT
> To: amber-spec-comments at openjdk.java.net
> 
> I want to propose one more design vector for enhanced string literals that
> I haven't seen before
> 
> Basically, I propose two extensions to get to multiline literals with
> incidental white space handling.
> 
> Extension1: allow sequences of string literals to denote a single
> concatenated literal
> Extension2: allow string literals that spans from an opening token till the
> end of a line
> 
> Let's start with an example:
> 
> String j = ""
>               + "public static void " + name + "(String... args) {\n"
>               + "    System.out.println(\"Hello,\\t\" +
> String.join(args));\n"
>               + "}\n";
> 
> Extension1: allow sequence of string literals to denote concatenated literal
> 
> With this extension we can get rid of plus operators, like this:
> 
> String j = ""
>              "public static void " + name + "(String... args) {\n"
>              "    System.out.println(\"Hello,\\t\" + String.join(args));\n"
>              "}\n";
> 
> This feature is not so alien, it is present in C language.
> It may seem not worth it, but I think it can be worth it in combination
> with second extension.
> 
> Extension2: allow string literals that spans from an opening token till the
> end of a line.
> 
> String s = "hello\n";
> 
> to be written as
> 
> String s =
>    """hello
>    ;
> 
> Tripple quotes in this case start a string literal which ends at an end of
> line.
> 
> Having these two extensions, we can rewrite our example as:
> 
> String j =
>      "public static void " + name + """(String... args) {
>    """    System.out.println("Hello,\\t" + String.join(args));
>    """}
>    ;
> 
> Other examples:
> 
> String sql =
>    """SELECT name
>    """FROM user
>    """WHERE id = ? and role = 'ADMIN'
>    ;
> 
> String json =
>    """{
>    """    "login": "john",
>    """    "id": 123.
>    """}
>    ;
> 
> String html =
>    """<div class="active">
>    """    <span class="title">Hello, World</span>
>    """</div>
>    ;
> 
> With this style we can't just copy and past snippets of foreign code into a
> string literal, but
> all we need is to prefix every line with tripple quotes.
> This style is analogues to source code comments handling by programmers,
> so, I think, it's familiar enough.
> 
>    // TODO: rewrite this method
>    // using new guava API
> 
> Automatic prefixing of comments is already present in every IDE and is
> simple enough to implement by hand, like
> 
>    | sed 's/^/"""/g'
> 
> Rawness can be added to such string literals independently in orthogonal
> way:
> 
> String regex = \"a(bc)+\s+(de|kg)?"\;
> 
> String j =
>       \"public static void "\ + name + \"""(String... args) {
>    \"""    System.out.println("Hello,\t" + String.join(args));
>    \"""}
>    ;
> 
> The problem I see is interoperability between simple string literals and
> "line sting literals": we can't easily align them vertically.
> But may be this problem is more easily solvable than magical incidental
> whitespace handling.
> 
> --
> Victor Nazarov

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