Hello,

I was wondering if there would be some way to verify arguments to a function at compile time, but at runtime call only one function (in D2).

To clarify what I mean:

Say you have something like printf()

printf(const char[] format, ...)

I want to be able to make sure the arguments passed into the varadic part match what the format string says at compile time. I could do this with a template, but then it generates a new printf() function for each combination of arguments, and I'm trying to avoid that. It might be possible to solve this with a mixin as well, but I'd like to avoid writing:

    mixin(SomeFunc!("args", t1, t2, t3))

(Maybe alias would be useful? My D skills aren't that great yet)

I would like it to be more like a regular function call

    SomeFunc("format", t1, t2) // Or something similar

If there's no good way to do this that's fine.

I bring this up because I saw

https://github.com/xomboverlord/xomb/blob/unborn/kernel/core/kprintf.d

which was neat, but it generates a new kprintf function for different arguments. I thought it'd be interesting to try and have the benefits of compile time checking without the extra generated code.

Thank you

DProgrammer2:

> If there's no good way to do this that's fine.
>
> I bring this up because I saw
>
> https://github.com/xomboverlord/xomb/blob/unborn/kernel/core/kprintf.d
>
> which was neat, but it generates a new kprintf function for different arguments. I thought it'd be interesting to try and have the benefits of compile time checking without the extra generated code.

I think currently there is no other way. Despite it's something I'd like a lot.

Someday I'd like a function like this in Phobos, that verifies the formatting string at compile-time:

ctwritefln!"%d %s"(5, "hello");

Such function can be written with just a very light wrapper around a normal writefln (and later to something more optimized). This means that the actual template bloat can be minimized a lot, but not fully removed.

Bye,
bearophile

On Fri, Jan 4, 2013 at 2:59 AM, bearophile <bearophileHUGS@lycos.com> wrote:

>
>> Someday I'd like a function like this in Phobos, that verifies the
> formatting string at compile-time:
>
> ctwritefln!"%d %s"(5, "hello");
>
> Such function can be written with just a very light wrapper around a normal writefln (and later to something more optimized). This means that the actual template bloat can be minimized a lot, but not fully removed.
>

You can find a partial version in a template tutorial I put on github.

https://github.com/PhilippeSigaud/D-templates-tutorial/

Select either of the .md, .pdf, .html or .epub version of the tutorial. It's section 5.11 "Statically-Checked Writeln".

The code worked the last time I launched the automated extractor/tester
(before 2.061).