Floating-point formatting string

Floating-point formatting string

[Vinicius Jose Latorre]

Hi,


It seems that there is a problem with floating-point formatting string 
in Emacs 22.

Type
   M-: (format "%03.3f" 1.2) RET
   ==> "1.200"

Shouldn't it be "001.200"?

   M-: (format "% 3.3f" 1.2) RET
   ==> " 1.200"

Shouldn't it be "  1.200"?

It's working for integer:

   M-: (format "%03d" 1) RET
   ==> "001"      ; OK

   M-: (format "% 3d" 1) RET
   ==> "  1"      ; OK


Vinicius

Re: Floating-point formatting string

[Juanma Barranquero]

On 2/14/07, Vinicius Jose Latorre <viniciusjl@ig.com.br> wrote:

> Type
>    M-: (format "%03.3f" 1.2) RET
>    ==> "1.200"
>
> Shouldn't it be "001.200"?

>From format's docstring:

  The basic structure of a %-sequence is
    % <flags> <width> <precision> character
  where flags is [- #0]+, width is [0-9]+, and precision is .[0-9]+

You're saying "flag = 0, width = 3, precision = 3". That overflows the
width = 3.

Try

  (format "%07.3f" 1.2) => "001.200"

             Juanma

Re: Floating-point formatting string

[Chong Yidong]

Vinicius Jose Latorre <viniciusjl@ig.com.br> writes:

> Hi,
>
>
> It seems that there is a problem with floating-point formatting string
> in Emacs 22.
>
> Type
>   M-: (format "%03.3f" 1.2) RET
>   ==> "1.200"
>
> Shouldn't it be "001.200"?

The Elisp manual says, of the width specification:

  If the printed representation of the object contains fewer
  characters than this width, then it is padded.

In this case, the 03 refers to the width of the entire string "1.200",
which is 5 > 3.

For example,

  M-: (format "%08.3f" 1.2)
  ==> 0001.200

Re: Floating-point formatting string

[Vinicius Jose Latorre]

Juanma Barranquero wrote:
> On 2/14/07, Vinicius Jose Latorre <viniciusjl@ig.com.br> wrote:
>
>> Type
>>    M-: (format "%03.3f" 1.2) RET
>>    ==> "1.200"
>>
>> Shouldn't it be "001.200"?
>
>> From format's docstring:
>
>  The basic structure of a %-sequence is
>    % <flags> <width> <precision> character
>  where flags is [- #0]+, width is [0-9]+, and precision is .[0-9]+
>
> You're saying "flag = 0, width = 3, precision = 3". That overflows the
> width = 3.
>
> Try
>
>  (format "%07.3f" 1.2) => "001.200"

Ok, width of ALL string representation.

I thought it was the integer part width only.


Thanks,


Vinicius

Re: Floating-point formatting string

[Vinicius Jose Latorre]

Chong Yidong wrote:
> Vinicius Jose Latorre <viniciusjl@ig.com.br> writes:
>
>   
>> Hi,
>>
>>
>> It seems that there is a problem with floating-point formatting string
>> in Emacs 22.
>>
>> Type
>>   M-: (format "%03.3f" 1.2) RET
>>   ==> "1.200"
>>
>> Shouldn't it be "001.200"?
>>     
>
> The Elisp manual says, of the width specification:
>
>   If the printed representation of the object contains fewer
>   characters than this width, then it is padded.
>
> In this case, the 03 refers to the width of the entire string "1.200",
> which is 5 > 3.
>
> For example,
>
>   M-: (format "%08.3f" 1.2)
>   ==> 0001.200
>   

Ok, thanks

Re: Floating-point formatting string

[Stuart D. Herring]

> In this case, the 03 refers to the width of the entire string "1.200",
which is 5 > 3.
>
> For example,
>
>   M-: (format "%08.3f" 1.2)
>   ==> 0001.200

That doesn't quite explain Vinicius' other examples; in particular,

M-: (format "% 3.3f" 1.2)
==> " 1.200"

which has been padded even though it's longer than 3 characters without
the space.

Davis

-- 
This product is sold by volume, not by mass.  If it appears too dense or
too sparse, it is because mass-energy conversion has occurred during
shipping.

Re: Floating-point formatting string

[Andreas Schwab]

"Stuart D. Herring" <herring@lanl.gov> writes:

> That doesn't quite explain Vinicius' other examples; in particular,
>
> M-: (format "% 3.3f" 1.2)
> ==> " 1.200"
>
> which has been padded even though it's longer than 3 characters without
> the space.

That's not padding, it's the sign. Similar to the '+' flag.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: Floating-point formatting string

[Juanma Barranquero]

On 2/14/07, Stuart D. Herring <herring@lanl.gov> wrote:

> That doesn't quite explain Vinicius' other examples; in particular,
>
> M-: (format "% 3.3f" 1.2)
> ==> " 1.200"
>
> which has been padded even though it's longer than 3 characters without
> the space.

That's not padding. The flag " " does not mean "pad with spaces", but
"inserts a space for positive numbers". That helps with columns, if
the number can also be negative:

ELISP> (format "%3.3f" 1.2)
"1.200"
ELISP> (format "%3.3f" -1.2)
"-1.200"
ELISP> (format "% 3.3f" 1.2)
" 1.200"
ELISP> (format "% 3.3f" -1.2)
"-1.200"

Space-padding is specified by using no flag:

ELISP> (format "%6.3f" -1.2)
"-1.200"
ELISP> (format "%6.3f" 1.2)
" 1.200"

             Juanma