Forum: Ruby Need help converting Perl to Ruby (detecting integers and de

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Paul (Guest)
on 2007-03-15 23:40
(Received via mailing list)
I am trying to convert a Perl script to Ruby and have been having some
difficulty along the way (mostly because I don't know Perl).

I am currently stumped on one particular line in the old Perl script:
---
  foreach (@rawfields) {if ($_ > 0){$_ = int($_*100)/100}}
---

Background context:  @rawfields is an array that holds the contents of
an imported line from a text file.  Here are some sample lines from
the input file:
---
"0"  "0"  "0"  "0"  "0"  "0"  "Bar"
"5.66666"  "0"  "3.566662"  "1.383332"  "6"  "0"  "Foo"
---

My guess is that the Perl line iterates through each of the elements
in the array and rounds any integers to 2 decimals.

This raises a few problems for me.

1) How can I easily tell if the (string) value in each array element
is an integer or has a decimal value?

=> The desired output for text file line 2 is :
---
"5.67"   "0"   "3.57"   "1.38"   "6"   "0"   "Foo"
---


I tried the following in Ruby:
---
@rawfields.each_index do |x|
  if ( @rawfields[x].to_f > 0 )
    @rawfields[x] = ( (( @rawfields[x].to_f * 100 ).round.to_i ).to_f /
100 ).to_s
  end
end
---

But it produces the following output:
---
"5.67"  "0"  "3.57"  "1.38"  "6.0"  "0"  "Foo"
---

...which is close, but not quite what I want.  My output file now has
values like 1.0, 5.0, 62.0, etc.  If it's an integer, I don't want to
see the decimal.

Can anyone suggest an improvement to my code or a better translation
from Perl?

TIA.  Paul.
Robert K. (Guest)
on 2007-03-15 23:56
(Received via mailing list)
On 15.03.2007 22:39, Paul wrote:
> the input file:
> 1) How can I easily tell if the (string) value in each array element
> @rawfields.each_index do |x|
> ---
>
> ...which is close, but not quite what I want.  My output file now has
> values like 1.0, 5.0, 62.0, etc.  If it's an integer, I don't want to
> see the decimal.
>
> Can anyone suggest an improvement to my code or a better translation
> from Perl?
>
> TIA.  Paul.
>

How about

irb(main):005:0> fields = %w{5.6666 0 Foo}
=> ["5.6666", "0", "Foo"]
irb(main):006:0> fields.map {|v| sprintf("%4.2f", Float(v)) rescue v}
=> ["5.67", "0.00", "Foo"]

This uses the fact that Float() will throw if the string is not a valid
number.  If you really need "0" instead of "0.00" you could apply
another test.  If you need the quotes you could do

irb(main):008:0> puts fields.map {|v| (sprintf("%4.2f", Float(v)) rescue
v).inspect}.join(" ")
"5.67" "0.00" "Foo"

Kind regards

  robert
Martin DeMello (Guest)
on 2007-03-15 23:59
(Received via mailing list)
On 3/16/07, Paul <removed_email_address@domain.invalid> wrote:
>
> Background context:  @rawfields is an array that holds the contents of
> an imported line from a text file.  Here are some sample lines from
> the input file:
> ---
> "0"     "0"     "0"     "0"     "0"     "0"     "Bar"
> "5.66666"       "0"     "3.566662"      "1.383332"      "6"     "0"     "Foo"

>> rawfields = ["5.66666", "0", "3.566662", "1.383332", "6", "0", "Foo"]
=> ["5.66666", "0", "3.566662", "1.383332", "6", "0", "Foo"]

>> rawfields.map {|field| "%0.2f" % Float(field) rescue field}
=> ["5.67", "0.00", "3.57", "1.38", "6.00", "0.00", "Foo"]

Breaking it up,

Float(string) either converts a string to a float, or raises an
exception if it cannot be so converted.

% is the sprintf operator, so "%0.2f" % float rounds the float to two
decimal places and interpolates it into the string. Note that it does
round properly, as per the printf spec, rather than truncating.

finally, expression1 rescue expression2 means return expression1,
unless it raises an exception in which case return expression2

martin
David A. Black (Guest)
on 2007-03-16 00:04
(Received via mailing list)
Hi --

On 3/15/07, Paul <removed_email_address@domain.invalid> wrote:
> the input file:
> 1) How can I easily tell if the (string) value in each array element
> @rawfields.each_index do |x|
> ---
>
> ...which is close, but not quite what I want.  My output file now has
> values like 1.0, 5.0, 62.0, etc.  If it's an integer, I don't want to
> see the decimal.
>
> Can anyone suggest an improvement to my code or a better translation
> from Perl?

See if this helps:

@rawfields.map! do |x|
  if x =~ /^\d+\.\d+$/
    "%.2f" % x
  else
    x
  end
end


David
Martin DeMello (Guest)
on 2007-03-16 00:06
(Received via mailing list)
On 3/16/07, Martin DeMello <removed_email_address@domain.invalid> wrote:
> => ["5.66666", "0", "3.566662", "1.383332", "6", "0", "Foo"]
>
> >> rawfields.map {|field| "%0.2f" % Float(field) rescue field}
> => ["5.67", "0.00", "3.57", "1.38", "6.00", "0.00", "Foo"]

oops - missed the fact that you didn't want integers converted into
decimals. Best way I can think of is a two level try/rescue-try/rescue

>> rawfields.map {|field| "%d" % Integer(field) rescue "%0.2f" %
Float(field) rescue field}
=> ["5.67", "0", "3.57", "1.38", "6", "0", "Foo"]

More explicitly

rawfields.map do |field|
  begin
    "%d" % Integer(field)
  rescue
    begin
        "%0.2f" % Float(field)
    rescue
       field
    end
  end
end

martin
Jon G. (Guest)
on 2007-03-16 00:22
(Received via mailing list)
rawfields.map { |f| f.to_f.to_s == f ? "%0.2f" % f.to_f : f }
=> ["5.67", "0", "3.57", "1.38", "6", "0", "Foo"]
Paul (Guest)
on 2007-03-16 04:56
(Received via mailing list)
That is brilliant!  Thank you, Jon!  Of all the good suggestions
posted, I like this one best.  You guys all rock!  Thanks so much for
the responses.

Cheers!  Paul. =)
Michael F. (Guest)
on 2007-03-16 05:23
(Received via mailing list)
On 3/16/07, Paul <removed_email_address@domain.invalid> wrote:
> That is brilliant!  Thank you, Jon!  Of all the good suggestions
> posted, I like this one best.  You guys all rock!  Thanks so much for
> the responses.
>
> Cheers!  Paul. =)
>
>
> On Mar 15, 6:22 pm, Jon G. wrote:
> > rawfields.map { |f| f.to_f.to_s == f ? "%0.2f" % f.to_f : f }

rawfields.map{|f| Integer(f) rescue Float(f) rescue f}
David A. Black (Guest)
on 2007-03-18 04:01
(Received via mailing list)
Hi --

On 3/15/07, Michael F. <removed_email_address@domain.invalid> wrote:
>
> rawfields.map{|f| Integer(f) rescue Float(f) rescue f}

That doesn't produce the desired output.


David
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