Poll on improved format strings.

[renoX]

Don Clugston a écrit :
> renoX wrote:
>> Hello,
>>
>> I've made a templated format string templates
>>
>> The idea is: printf format string are interesting because they are 
>> powerful but they suck because the %d,%s, etc are in one part of the 
>> function and the corresponding variable are in a different part of the 
>> function (Tango has the same problem), writef improve this by allowing 
>> "... %d",var," ... %s",var2 but it's still not ideal because in the 
>> gluing of the various strings, it's easy to forget a space or a comma 
>> thus providing a not very good output.
>>
>> So my idea would be to have embedded expression like this "... 
>> %08d{var1+var2} ...", but it's not easy to provide a good 
>> syntax/semantic, so I'd like some remarks:
> 
> I like this better than anything else I've ever seen.
> 
>>
>> -Should the mix of printf format and new style format string be 
>> allowed? (It is in the current implementation).
>> This has the advantage of nearly keeping  the compatibility, the 
>> problem is with the format string "..%d{..." in printf this means a 
>> number followed by '{' but with the new format this creates an error.
>> It is possible to escape the '{' to allow this, ie to say that '%{' is 
>> '{' so now '%d{' would need to be '%d%{', this has the inconvenient 
>> that it's not possible to have the embedding format '%{var}' which 
>> would be the shortest syntax..
>> Another possibility would be to say that if you want to have '... %d{ 
>> ...' one need to write it has '.... %d',var,'{ ....', this would 
>> permit to have the '..%{var}...' embedding syntax.
> 
> Personally I'd rather get an error if I leave off the {}.
> (I'm someone who uses {} inside printf debugging strings a lot, so it's 
> far from compatible for me).
> I think it's better to minimise features wherever possible.

And this has the benefit that %{var} is the 'default' embedded format 
string no need to use %s{var}.
 >
>> -What to do with non-const char[]?
> 
> Aren't they a security risk?
> eg,
> char [] a  = getFromUser();
> writefln(a);

Yes, they might be a security risk if they are not 'sanitized' before usage.

> 
> if a is "%d", you get an access violation. Apart from security, it just 
> hides an insidious bug -- the code works fine until someone innocently 
> enters a % followed by one of the allowable letters....
> I've always thought that the first argument to printf() should be forced 
> to be a string literal.
> I would see it as an *advantage*, to only support const char [] !

Interesting.
Thanks for sharing your opinion, it's true that supporting only
const char[] and the 'embedded format string' makes the usage of 
putf/sputf easier for the programmer..

I think that I will follow your ideas.

Regards,
renoX