DIP 1027---String Interpolation---Community Review Round 1

[Patrick Schluter]

On Monday, 16 December 2019 at 10:48:51 UTC, aliak wrote:
> On Monday, 16 December 2019 at 01:35:51 UTC, Walter Bright 
> wrote:
>> On 12/15/2019 2:17 AM, Aliak wrote:
>>> To use it people will need to understand how to use d tuples 
>>> as well.
>>
>> No, they don't.
>
> User: why can't I do this?/Why doesn't this work?
>
> string s = i"$var";
>
> Answer?

because

string s = ("%s",var);

is a syntax error. Even a beginning programmer can understand 
that an interpolated string cannot be a pure simple string as it 
contains symbols and expressions that are language construct not 
part of the string literal, i.e. that the compiler has to perform 
some transformations to substitute these language symbols into a 
value.
Interpolated strings, in any language, are not string literals. 
Each language resolves this fact in different manners and at 
different times. Interpreted languages do it at runtime 
(obviously), java like languages chose to do it at runtime. In a 
language like D, which prefers resolving what is resolvable at 
compile time, it would be loathed if it interpolation was 
resolved at runtime (remember how long people were bitching about 
runtime only format strings?)
Resolving interpolation at compile time is imho incompatible with 
handling them as regular strings.

The question is then do we want CT or RT interpolated strings. RT 
interpolated strings can still be provided by a library.