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

[Alexandru Ermicioi]

On Saturday, 14 December 2019 at 07:34:05 UTC, Walter Bright 
wrote:
> On 12/11/2019 2:57 AM, Alexandru Ermicioi wrote:
>> Why not just split interpolated string into just a tuple of 
>> args & strings. For example:
>> Given: (i"I ate %apples and %bananas totalling %(apples + 
>> bananas) fruit.")
>> Is lowered to a tuple: ("I ate ", apples, " and ", bananas," 
>> totalling ", apples + bananas," fruit.")
>
> I don't see the point of that. The user could write it that way 
> to begin with.

Yes he could. The main concern I have is that current proposal is 
tied to printf syntax (template string first, and then args to 
replace) which will be quite cumbersome for people who would like 
to use tuple resulting from interpolation. They will need to 
parse template string to find all args placeholders and then 
split template string on those locations in most basic case. This 
is unnecessary boilerplate code thrown onto user. Example above 
solves this issue by removing the need to parse this template 
string since it won't be there anymore. In any case Adam's 
version seems more versatile and could work nicely, allowing user 
to choose what he would get from interpolation. For example it 
could alias itself to a built version of interpolated string, and 
expose interface to get interpolated tuple in printf format, or 
in format suitable for text function. Also having such structure 
we could encode other information such as variable prefix syntax 
used in interpolation string if it is decided to have the ability 
to change prefix, which could be then used nicely to throw 
asserts on wrong interpolation syntax being used and etc.

The only thing is I don't understand why a struct is not 
sufficient for interpolated string  in Adam's proposal.

Best regards,
Alexandru