zero placeholder exponential sprintf?

[Bil Kleb]

Hi,

We have a request for 0.112345e+02 instead of,

% ruby -e "puts '%.6e' % [ 1.123450e+2 ]"
1.123450e+02

Possible?

Thanks,
--
Bil Kleb
http://fun3d.larc.nasa.gov

[7stud --]

Bil Kleb wrote:
> Hi,
>
> We have a request for 0.112345e+02 instead of,
>
> % ruby -e "puts '%.6e' % [ 1.123450e+2 ]"
> 1.123450e+02
>
> Possible?
>
> Thanks,

data = 112.3450
result = "%e" % [data]

puts result #1.123450e+02

pieces = result.split(".")
result = ".%s" % [pieces.join()]

puts result
--output:--
1123450e+02

Of course, it wouldn't make any sense to do that.

--
Posted via http://www.ruby-forum.com/.

[Harry Kakueki]

I may be missing what you are after, but....
Does it need to be sprintf?

require 'bigdecimal'
p BigDecimal.new(1.12345e+2.to_s).to_s #=> "0.112345E3"

Harry

--
A Look into Japanese Ruby List in English
http://www.kakueki.com/ruby/list.html

[Bil Kleb]

Harry Kakueki wrote:
> On Wed, Aug 5, 2009 at 7:00 AM, Bil Kleb<Bil....@nasa.gov> wrote:

>> We have a request for 0.112345e+03 instead of,

>>
>> % ruby -e "puts '%.6e' % [ 1.123450e+2 ]"
>> 1.123450e+02

> I may be missing what you are after, but....

> Does it need to be sprintf?

Sorry for the confusion, String::% uses Kernel::sprintf -- see

http://www.ruby-doc.org/core/classes/String.html#M000770

So, to match my subject line better and correct the desired
formatted number:

ruby -e "puts sprintf('%.6e',1.123450e+2)" #=> 1.123450e+02

but I want '0.112345e+03', i.e., a leading zero placeholder.

@drbrain says this probably violates IEEE,

http://twitter.com/drbrain/statuses/3132296591
http://twitter.com/drbrain/statuses/3132322954

> require 'bigdecimal'
> p BigDecimal.new(1.12345e+2.to_s).to_s #=> "0.112345E3"

Hmmm, now just need the '+0' part in the exponent and control
of the number of decimal places?

Regards,

[Harry Kakueki]

>
> ruby -e "puts sprintf('%.6e',1.123450e+2)" #=> 1.123450e+02
>
> but I want '0.112345e+03', i.e., a leading zero placeholder.
>

> Hmmm, now just need the '+0' part in the exponent and control
> of the number of decimal places?
>

I am still not sure if you require sprintf.
I am not familiar with that but I will learn about it starting tomorrow. Thanks.

This code looks a bit strange to me and it is not very DRY.
Maybe someone will have a better solution soon. There must be a better way.
It may have some problems, so check it carefully. It is the best I can
offer you this late at night.

x = 1.12345e2

sig,y = 9, Math.log10(x).floor + 1
p (x*10**(y*-1)).to_s[0..sig+1].ljust(sig+2,"0") + "e+" +
y.to_s.rjust(2,"0") if y >= 0
p (x*10**(y*-1)).to_s[0..sig+1].ljust(sig+2,"0") + "e-" +
y.abs.to_s.rjust(2,"0") if y < 0

[Brian Candler]

Bil Kleb wrote:
> Hi,
>
> We have a request for 0.112345e+02 instead of,
>
> % ruby -e "puts '%.6e' % [ 1.123450e+2 ]"
> 1.123450e+02
>
> Possible?
>
> Thanks,

I'm not sure this works for all possible cases, but you could just
manipulate the string a bit:

class Float
def fmt(prec=6)
str = "%.*e" % [prec-1, self]
if str =~ /^([1-9])\.(\d+)e([+-])(\d+)$/
str = "0.%s%se%s%02d" % [$1,$2,$3,$4.to_i]
end
str
end
end

a = 1.123450e+2
puts a.fmt

[Harry Kakueki]

On Wed, Aug 5, 2009 at 10:57 PM, Harry Kakueki<list...@gmail.com> wrote:
>>
>
> x = 1.12345e2
>
> sig,y = 9, Math.log10(x).floor + 1
> p (x*10**(y*-1)).to_s[0..sig+1].ljust(sig+2,"0") + "e+" +
> y.to_s.rjust(2,"0") if y >= 0
> p (x*10**(y*-1)).to_s[0..sig+1].ljust(sig+2,"0") + "e-" +
> y.abs.to_s.rjust(2,"0") if y < 0
>
>
> Harry
>

This is the same code I posted earlier, just a little DRYer.

x = 1.12345e2

s,y,h = 7, Math.log10(x).floor+1,{-1=>"-",0=>"+",1=>"+"}
p (x*10**(y*-1)).to_s[0..s+1].ljust(s+2,"0")+"e"+h[(y<=>0)]+y.abs.to_s.rjust(2,"0")

[Harry Kakueki]

>
> We have a request for 0.112345e+02 instead of,
>
> % ruby -e "puts '%.6e' % [ 1.123450e+2 ]"
> 1.123450e+02
>
> Possible?
>

Sorry for posting yet again.
Just a little adjustment.
I'll stop now.

x = 1.12345e2

s,y,h = 7, Math.log10(x).floor+1,{-1=>"e-",0=>"e+",1=>"e+"}
p (x*10**(y*-1)).to_s[0..s+1].ljust(s+2,"0")+h[(y<=>0)]+y.abs.to_s.rjust(2,"0")

[7stud --]

Bil Kleb wrote:
>
> Sorry for the confusion, String::% uses Kernel::sprintf -- see
>
> http://www.ruby-doc.org/core/classes/String.html#M000770
>

Uh, no.

class Object
def sprintf(*args)
puts "inside sprintf..."
"hello"
end
end

result = sprintf("%.6e", 1.123450e4)
puts result

puts "%.6e" % 1.123450e4

--output:--
inside sprintf...
hello
1.123450e+04