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

[Scott McKellar]

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

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