Re: Orphan format arguments: args[0..1]

[bauss via Digitalmars-d-learn]

On Sunday, 16 December 2018 at 00:34:48 UTC, Ali Çehreli wrote:
This one confused me until I decided to talk to a rubber ducky:
import std.string;

void main() {
    auto s = "%s is a good number".format(42);
}

Fine; it works... Then the string becomes too long and I split 
it:

    auto s = "%s is a good number but one needs to know" ~
             " what the question exactly was.".format(42);

Now there is a compilation error:

  Orphan format arguments: args[0..1]

What? Is that a bug in format? It can't be because the string 
should be concatenated by the compiler as a single string, no? 
No: operator dot has precedence over ~, so format is applied to 
the second part of the string before the concatenation. Doh! 
This puzzled me a lot.

Anyway, the solution, once again, is to use parentheses:

    auto s = ("%s is a good number but one needs to know" ~
              " what the question exactly was.").format(42);

Ali

The reason it doesn't work in the second example is because it 
translates to something like this:

auto s = "%s is a good number but one needs to know" ~ ("what the 
question exactly was.".format(42));

The reason encapsulation the two strings works is because you 
append the second string to the first before you call format.

Definitely not a bug.