[lnkForumImage]
TotalShareware - Download Free Software
Confronta i prezzi di migliaia di prodotti.
Asp Forum
 Home | Login | Register | Search 


 

Forums >

comp.lang.ruby

Where do I put the ".to_f" ?

Peter Bailey

1/7/2008 6:06:00 PM

Hello,
I need to do some simply computations on numbers pulled from a file. I
get the numbers using "scan." I've proven that I can get the numbers
alright. But, I need to do some division and multiplication on those
numbers, and, to be accurate, the numbers need to be floating numbers,
not integers. So, I've tried everything, or so I think, and Ruby keeps
complaining about my ".to_f" method. Can someone please tell me where
this .to_f should go?
Thanks,
Peter

Dir.chdir("K:")
tifffile = File.basename(ARGV.to_s, ".*") + ".tif"
info = `tiffinfo #{tifffile}`
width = info.scan(/Image Width: ([0-9]{1,5})/)
depth = info.scan(/Image Length: ([0-9]{1,5})/)
res = info.scan(/Resolution: [0-9]{1,5}, ([0-9]{1,5}) pixels\/inch/)

newwidth = width.to_f / 600 * 6
newdepth = depth.to_f / 600 * 6

I get this from Ruby:
sizer.rb:10: undefined method `to_f' for [["5100"]]:Array
(NoMethodError)
--
Posted via http://www.ruby-....
13 Answers

Robert Klemme

1/7/2008 6:13:00 PM

0

On 07.01.2008 19:06, Peter Bailey wrote:
> Hello,
> I need to do some simply computations on numbers pulled from a file. I
> get the numbers using "scan." I've proven that I can get the numbers
> alright. But, I need to do some division and multiplication on those
> numbers, and, to be accurate, the numbers need to be floating numbers,
> not integers. So, I've tried everything, or so I think, and Ruby keeps
> complaining about my ".to_f" method. Can someone please tell me where
> this .to_f should go?
> Thanks,
> Peter
>
> Dir.chdir("K:")
> tifffile = File.basename(ARGV.to_s, ".*") + ".tif"
> info = `tiffinfo #{tifffile}`
> width = info.scan(/Image Width: ([0-9]{1,5})/)
> depth = info.scan(/Image Length: ([0-9]{1,5})/)
> res = info.scan(/Resolution: [0-9]{1,5}, ([0-9]{1,5}) pixels\/inch/)
>
> newwidth = width.to_f / 600 * 6
> newdepth = depth.to_f / 600 * 6
>
> I get this from Ruby:
> sizer.rb:10: undefined method `to_f' for [["5100"]]:Array
> (NoMethodError)

Your error is in using #scan (see the docs for details).

This works better

width = info[/Image Width: ([0-9]{1,5})/, 1].to_f
....

Cheers

robert

Oliver Saunders

1/7/2008 6:15:00 PM

0

> Ruby keeps complaining about my ".to_f" method.

What does it say?

I thought initially that you could have some extra whitespace in your
strings but it seems Ruby is pretty tolerant about this stuff:

irb(main):001:0> '5.0'.to_f
=> 5.0
irb(main):002:0> ' 5.0 '.to_f
=> 5.0
irb(main):003:0> ' 5.0a '.to_f
=> 5.0
irb(main):004:0> 'a5.0'.to_f
=> 0.0
--
Posted via http://www.ruby-....

Daniel Finnie

1/7/2008 6:21:00 PM

0

[Note: parts of this message were removed to make it a legal post.]

Scan is generally used when you have multiple matches, for example
"abcdefg".scan(/../) => ["ab", "cd", "ef"].

I think in your case match is better:
Dir.chdir("K:")
tifffile = File.basename(ARGV.to_s, ".*") + ".tif"
info = `tiffinfo #{tifffile}`
width = info.match(/Image Width: ([0-9]{1,5})/)[1]
depth = info.match(/Image Length: ([0-9]{1,5})/)[1]
res = info.match(/Resolution: [0-9]{1,5}, ([0-9]{1,5}) pixels\/inch/)[1]

newwidth = width.to_f / 600 * 6
newdepth = depth.to_f / 600 * 6

And now your code should work as intended. The [1] at the end of the match
is because match returns an object that can act like an Array of [the whole
match, the first parenthesis, the second parenthesis, etc...].

The reason you were getting an error before is that you were calling to_f on
an Array. [4].to_f might be interpreted by a human as 4.to_f but not to
Ruby. And what would ruby do if it was [2, 3, 4].to_f ?

Dan

On 1/7/08, Peter Bailey <pbailey@bna.com> wrote:
>
> Hello,
> I need to do some simply computations on numbers pulled from a file. I
> get the numbers using "scan." I've proven that I can get the numbers
> alright. But, I need to do some division and multiplication on those
> numbers, and, to be accurate, the numbers need to be floating numbers,
> not integers. So, I've tried everything, or so I think, and Ruby keeps
> complaining about my ".to_f" method. Can someone please tell me where
> this .to_f should go?
> Thanks,
> Peter
>
> Dir.chdir("K:")
> tifffile = File.basename(ARGV.to_s, ".*") + ".tif"
> info = `tiffinfo #{tifffile}`
> width = info.scan(/Image Width: ([0-9]{1,5})/)
> depth = info.scan(/Image Length: ([0-9]{1,5})/)
> res = info.scan(/Resolution: [0-9]{1,5}, ([0-9]{1,5}) pixels\/inch/)
>
> newwidth = width.to_f / 600 * 6
> newdepth = depth.to_f / 600 * 6
>
> I get this from Ruby:
> sizer.rb:10: undefined method `to_f' for [["5100"]]:Array
> (NoMethodError)
> --
> Posted via http://www.ruby-....
>
>

Peter Bailey

1/7/2008 6:25:00 PM

0

Robert Klemme wrote:
> On 07.01.2008 19:06, Peter Bailey wrote:
>>
>> I get this from Ruby:
>> sizer.rb:10: undefined method `to_f' for [["5100"]]:Array
>> (NoMethodError)
>
> Your error is in using #scan (see the docs for details).
>
> This works better
>
> width = info[/Image Width: ([0-9]{1,5})/, 1].to_f
> ...
>
> Cheers
>
> robert

Thank you very much. Yes, that works perfectly. That whole square
bracket thing you use there is new to me. When you say "see the docs,"
what should I look for? For "String#scan" or for Regex. . . .?
--
Posted via http://www.ruby-....

Todd Benson

1/7/2008 6:38:00 PM

0

On Jan 7, 2008 12:25 PM, Peter Bailey <pbailey@bna.com> wrote:
> Robert Klemme wrote:
> > On 07.01.2008 19:06, Peter Bailey wrote:
> >>
> >> I get this from Ruby:
> >> sizer.rb:10: undefined method `to_f' for [["5100"]]:Array
> >> (NoMethodError)
> >
> > Your error is in using #scan (see the docs for details).
> >
> > This works better
> >
> > width = info[/Image Width: ([0-9]{1,5})/, 1].to_f
> > ...
> >
> > Cheers
> >
> > robert
>
> Thank you very much. Yes, that works perfectly. That whole square
> bracket thing you use there is new to me. When you say "see the docs,"
> what should I look for? For "String#scan" or for Regex. . . .?

You want to look at String#[]

Todd

Sebastian Hungerecker

1/7/2008 6:42:00 PM

0

Peter Bailey wrote:
> Dir.chdir("K:")
> tifffile = File.basename(ARGV.to_s, ".*") + ".tif"

So "yourscript.rb c:/foo/bar.jpg" would open the file k:/bar.tif? That
seems... wrong to me. But of course I don't know why you do this - it
might make perfect sense under the circumstances.


> info = `tiffinfo #{tifffile}`
> width = info.scan(/Image Width: ([0-9]{1,5})/)

String#scan creates an array of strings (if you have a regex without capturing
groups) or of arrays (where for each capturing group you have a string in the
array). For example:

"foo123bar456chunky789bacon".scan(/\d+/) #=> ["123","456","789"]
"hi:ho foo:bar".scan(/(\w+):(\w+)/) #=> [["hi","ho"], ["foo","bar"]]
"Image Width: 123".scan(/Image Width: ([0-9]{1,5})/) #=> [["123"]]

That's an array containing an array containing a string. Since you just want
the string and since there's only ever gonna be one, you should just use
String#match or String#[]:

width = info[/Image Width: ([0-9]{1,5})/, 1]

If String#[] is used with a regex it will return the substring matching that
regex. If you also give it a number as second argument, it will only return
the contents of the nth capturing group (n being the number).


> I get this from Ruby:
> sizer.rb:10: undefined method `to_f' for [["5100"]]:Array
> (NoMethodError)

Yes, arrays don't have a to_f method (since arrays usually contain multiple
elements and it would be strange to turn that into one single number).
If you use [] like I showed above, you will have a string, which will have a
to_f method, so this will work.


HTH,
Sebastian
--
Jabber: sepp2k@jabber.org
ICQ: 205544826

Daniel Finnie

1/7/2008 6:44:00 PM

0

[Note: parts of this message were removed to make it a legal post.]

String#scan as you are calling the scan method of a string instance. String
is known as the receiver.

Dan

On 1/7/08, Peter Bailey <pbailey@bna.com> wrote:
>
> Robert Klemme wrote:
> > On 07.01.2008 19:06, Peter Bailey wrote:
> >>
> >> I get this from Ruby:
> >> sizer.rb:10: undefined method `to_f' for [["5100"]]:Array
> >> (NoMethodError)
> >
> > Your error is in using #scan (see the docs for details).
> >
> > This works better
> >
> > width = info[/Image Width: ([0-9]{1,5})/, 1].to_f
> > ...
> >
> > Cheers
> >
> > robert
>
> Thank you very much. Yes, that works perfectly. That whole square
> bracket thing you use there is new to me. When you say "see the docs,"
> what should I look for? For "String#scan" or for Regex. . . .?
> --
> Posted via http://www.ruby-....
>
>

Peter Bailey

1/7/2008 7:36:00 PM

0

Sebastian Hungerecker wrote:

>
> Yes, arrays don't have a to_f method (since arrays usually contain
> multiple
> elements and it would be strange to turn that into one single number).
> If you use [] like I showed above, you will have a string, which will
> have a
> to_f method, so this will work.
>
>
> HTH,
> Sebastian

This is very cool, what you've shown me here. I've never used the
String#[] nomenclature before, especially, with the number argument in
it. It's so simple! Thanks!
--
Posted via http://www.ruby-....

Peter Bailey

1/7/2008 7:37:00 PM

0

Daniel Finnie wrote:
> String#scan as you are calling the scan method of a string instance.
> String
> is known as the receiver.
>
> Dan

Thanks !
--
Posted via http://www.ruby-....

Peter Bailey

1/7/2008 7:39:00 PM

0

Todd Benson wrote:
> On Jan 7, 2008 12:25 PM, Peter Bailey <pbailey@bna.com> wrote:
>> >
>> > width = info[/Image Width: ([0-9]{1,5})/, 1].to_f
>> > ...
>> >
>> > Cheers
>> >
>> > robert
>>
>> Thank you very much. Yes, that works perfectly. That whole square
>> bracket thing you use there is new to me. When you say "see the docs,"
>> what should I look for? For "String#scan" or for Regex. . . .?
>
> You want to look at String#[]
>
> Todd

Yes. Thanks. It's just that I never knew that String#[] even existed.
It's a great tool.

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