[phobos] expand for std.metastrings

[kenji hara]

1) Appender does not work at compile time.
2) I assume that interp is mainly used for code generation.
    So, I think the cost of implementing and the purpose are incongruous.

Kenji

2010/11/2 Andrei Alexandrescu <andrei at erdani.com>:
> One more thing - for efficiency, instead of using to!string, I suggest you
> use formattedWrite with "%s" as format string and an appender as writer.
>
> Andrei
>
> On 11/2/10 5:40 AM, kenji hara wrote:
>>
>> Thanks for your response, Andrei.
>>
>> I applied improvements that suggested from you.
>> - Identifier expression currently does not require braces.
>> - Interpolation expression is converted to string implicitly (with
>> std.conv.to!string(...)).
>>
>> It is still not renamed to 'inter' in github, but I would to do it
>> when committing to Phobos.
>>
>> Kenji Hara
>>
>> 2010/11/2 Andrei Alexandrescu<andrei at erdani.com>:
>>>
>>> This is great. It's funny I was thinking the same this morning before
>>> having
>>> looked over this message.
>>>
>>> As expansion using $xxx is called interpolation in Perl and probably
>>> other
>>> scripting languages I suggest we call the facility "inter".
>>>
>>> We can use it with writeln, which I think will be quite popular:
>>>
>>> int a = 2;
>>> string b = "hello";
>>> writeln(mixin(inter!"I told you $a times: $str!"));
>>>
>>> As shown above, I also suggest that we don't require {} when the
>>> expression
>>> is an identifier.
>>>
>>> A debatable language change would allow us to eliminate "mixin", as it
>>> has
>>> been discussed in the newsgroup. A simpler and less dangerous change
>>> would
>>> be to make the paren optional:
>>>
>>> writeln(mixin inter!"I told you $a times: $str!");
>>>
>>>
>>>
>>> Andrei
>>>
>>> On 10/31/10 10:50 AM, kenji hara wrote:
>>>>
>>>> I wrote a trivial utility template for generating code string.
>>>> This provides some easiness and viewability of metaprogramming.
>>>> (This is currently used in my adaptTo.)
>>>>
>>>> http://github.com/9rnsr/scrap/blob/master/expand/expand.d
>>>>
>>>> Sample:
>>>> ----
>>>> template GenFunc(string name)
>>>> {
>>>>   mixin(
>>>>     mixin(expand!q{
>>>>       int ${name}(){ return 10; }
>>>>     }));
>>>>   // result of expand! is:
>>>>   //   q{`int ` ~ name ~ `(){ return 10; }`}
>>>> }
>>>> mixin GenFunc!("test");   // generates function "test" returns int
>>>> unittest{
>>>>   assert(test() == 10);
>>>> }
>>>> ----
>>>>
>>>> expand!q{ codes... } parses D code string, and expands ${ expr } for
>>>> embedding expr that is expression evaluated as string in compile-time.
>>>>
>>>> do you think?
>>>>
>>>> Kenji
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