[OPEN-ILS-DEV] C nits: invalid conversion specification

[Joe Atzberger]

Perl accepts it inasmuch as it doesn't consider it an error (even under warnings and strict).  The typical error message 
would be (for example, with %j):
	Invalid conversion in printf: "%j"

I agree there doesn't seem to be any reason to use "%lf" in perl either, since apparently all floating point formatting 
gets handed off to the C sprintf.

--Joe

Scott McKellar wrote:
> What is your basis for saying that Perl accepts "%lf" for printf
> and sprintf?
> 
> I looked at the link you provided, and I looked in the camel book
> (which has much of the same verbiage), and I don't see any indication 
> that "%lf" is valid in Perl.  
> 
> Given that Perl relies on the C library to format floating point
> numbers, one of three things must be happening:
> 
> 1. Perl silently removes the extraneous 'l' before passing the
> conversion specification to the C library, or:
> 
> 2. It doesn't, and whatever happens happens, depending on what the
> C library does on a give platform, or:
> 
> 3. It issues an error or warning message, and possibly takes either
> of the above actions as well.
> 
> I just experimented with a test script using "%lf" and perl didn't
> complain, even with the -w option.  So the third possibility above
> appears not to be happening.
> 
> In any case, it seems like there's no good reason to use "%lf" in
> Perl, any more than in C.
> 
> Disclaimer: my knowledge of Perl doesn't extend much beyond how to
> spell it.
> 
> Scott McKellar
> http://home.swbell.net/mck9/aargh/
> 
> 
> --- Joe Atzberger <atzberger at MECDC.ORG> wrote:
> 
>> Perl accepts "%lf" as an accepted format for printf and sprintf.  It
>> would only be particularly meaningful on a system 
>> where the default size of a floating point number was not long double
>> (i.e., double or quad).
>>
>>  From perldoc:
>> 	http://perldoc.perl.org/functions/sprintf.html
>>    "For floating point conversions (e f g E F G), numbers are usually
>> assumed to be the default floating point size on 
>> your platform (double or long double), but you can force 'long
>> double' with q, L , or ll if your platform supports them."
>>
>> Interestingly, this may conflict with the fact that perl's sprintf
>> actually invokes the C version for floating point 
>> numbers:
>>    "Perl does its own sprintf formatting--it emulates the C function
>> sprintf, but it doesn't use it (*except for 
>> floating-point numbers*, and even then only the standard modifiers
>> are allowed)."
>>
>> So based on that, I'm more confused than anything.  It seems like it
>> should only be a question of what the C version 
>> supports for floats, even if perl doesn't report a warning/error.
>>
>> --Joe Atzberger
>> INFOhio Technical Specialist
>> Metropolitan Educational Council
>> (614) 473-8300 x22
>> atzberger at mecdc.org
> 
> <snip>