Scanning a string for decimal numbers

ruby-talk
1

Hi all, how do you scan a string and avoid getting my decimal numbers
divided into 2 numbers.

Example:

a = "24,4 + 55,2"
a.scan! (/\d+/)
puts a

my output for a will be:
24
4
55
2

But I want to keep my decimal numbers intact like this:
24,4
55,2

How do I solve this problem without putting the numbers into seperate
strings?

2

"24,4 + 55,2".scan /[\d,]+/

Kent

···

On 2/4/06, Jeppe Jakobsen <jeppe88@gmail.com> wrote:

Hi all, how do you scan a string and avoid getting my decimal numbers
divided into 2 numbers.

Example:

a = "24,4 + 55,2"
a.scan! (/\d+/)
puts a

my output for a will be:
24
4
55
2

But I want to keep my decimal numbers intact like this:
24,4
55,2

How do I solve this problem without putting the numbers into seperate
strings?

3

Jeppe Jakobsen wrote:

Hi all, how do you scan a string and avoid getting my decimal numbers
divided into 2 numbers.

Example:

a = "24,4 + 55,2"
a.scan! (/\d+/)
puts a

my output for a will be:
24
4
55
2

But I want to keep my decimal numbers intact like this:
24,4
55,2

How do I solve this problem without putting the numbers into seperate
strings?

Hi Jeppe,
you can use the following:

a.scan /[-+]?[0-9]*\,?[0-9]+/

which will take care of negative numbers as well.

HTH,
Antonio

···

--
Zen and the Art of Ruby Programming

4

This should handle periods or commas as the separator.

a = "24,4 + 55,2 + 55 - 44,0"
   => "24,4 + 55,2 + 55 - 44,0"
a.scan /(\d+,?.?\d*)(?=\s|$)/
   => [["24,4"], ["55,2"], ["55"], ["44,0"]]

···

On 2/4/06, Jeppe Jakobsen <jeppe88@gmail.com> wrote:

Hi all, how do you scan a string and avoid getting my decimal numbers
divided into 2 numbers.

Example:

a = "24,4 + 55,2"
a.scan! (/\d+/)
puts a

my output for a will be:
24
4
55
2

But I want to keep my decimal numbers intact like this:
24,4
55,2

How do I solve this problem without putting the numbers into seperate
strings?

5

Kent Sibilev wrote:

"24,4 + 55,2".scan /[\d,]+/

Kent

Hi all, how do you scan a string and avoid getting my decimal numbers
divided into 2 numbers.

Example:

a = "24,4 + 55,2"
a.scan! (/\d+/)
puts a

my output for a will be:
24
4
55
2

But I want to keep my decimal numbers intact like this:
24,4
55,2

How do I solve this problem without putting the numbers into seperate
strings?

try
a.scan!(/\d+,\d+/)
Ernie

···

On 2/4/06, Jeppe Jakobsen <jeppe88@gmail.com> wrote:

--
"Keep an open mind, but not so open that your brain falls out." (Richard Feynman)

6

a.scan /[-+]?[0-9]*\,?[0-9]+/

Or to be less verbose you can use \d in place of [0-9] :slight_smile:

HTH
Antonio

···

--
Zen and the Art of Ruby Programming

7

Hi!

···

At Sun, 05 Feb 2006 11:43:52 +0000, Antonio Cangiano wrote:

a.scan /[-+]?[0-9]*\,?[0-9]+/

Shouldn't that rather be the following?

a.scan /[-+]?([1-9]\d*(\,[0-9]+)?)|(0(\,[0-9]+)?)/

Josef 'Jupp' Schugt
--
Let the origin be the middle of the earth, p(x,r) be the probability
density for finding person x at distance r. Make sure that a permanent
solution of int_0^R p(x,r) dr < 1 exists for R being the instantanous
value of the distance between earth and mars.

8

Nice, that was the thing I was looking for :slight_smile:

···

2006/2/12, Wilson Bilkovich <wilsonb@gmail.com>:

On 2/4/06, Jeppe Jakobsen <jeppe88@gmail.com> wrote:
> Hi all, how do you scan a string and avoid getting my decimal numbers
> divided into 2 numbers.
>
> Example:
>
> a = "24,4 + 55,2"
> a.scan! (/\d+/)
> puts a
>
> my output for a will be:
> 24
> 4
> 55
> 2
>
> But I want to keep my decimal numbers intact like this:
> 24,4
> 55,2
>
>
> How do I solve this problem without putting the numbers into seperate
> strings?
>
This should handle periods or commas as the separator.

a = "24,4 + 55,2 + 55 - 44,0"
   => "24,4 + 55,2 + 55 - 44,0"
a.scan /(\d+,?.?\d*)(?=\s|$)/
   => [["24,4"], ["55,2"], ["55"], ["44,0"]]

9

This should handle periods or commas as the separator.

a = "24,4 + 55,2 + 55 - 44,0"
   => "24,4 + 55,2 + 55 - 44,0"
a.scan /(\d+,?.?\d*)(?=\s|$)/
   => [["24,4"], ["55,2"], ["55"], ["44,0"]]

Some problems here:
- signs are disregarded ("-24,4" becomes "24,4")
- Invalid numbers are accepted: eg. "24,.4" "24,." "24." "24,"
- "." should be escaped. As you used it here, it means "any character"
(except newline), so many invalid numbers are accepted (e.g. "24w"...)
- If something different from whitespace follows the number, it is not
or false accepted, e.g. "24.4." becomes "4." instead of "24.4"
- ...

Alexis.

10

careful. you'll kill negatives.

-a

···

On Sun, 5 Feb 2006, Ernest Ellingson wrote:

Kent Sibilev wrote:

"24,4 + 55,2".scan /[\d,]+/

Kent

On 2/4/06, Jeppe Jakobsen <jeppe88@gmail.com> wrote:

Hi all, how do you scan a string and avoid getting my decimal numbers
divided into 2 numbers.

Example:

a = "24,4 + 55,2"
a.scan! (/\d+/)
puts a

my output for a will be:
24
4
55
2

But I want to keep my decimal numbers intact like this:
24,4
55,2

How do I solve this problem without putting the numbers into seperate
strings?

try
a.scan!(/\d+,\d+/)
Ernie

--
happiness is not something ready-made. it comes from your own actions.
- h.h. the 14th dali lama

11

If you have Perl installed, the incantation

     perldoc -q float

gives some regexps for numbers.

-- fxn

···

On Feb 5, 2006, at 13:03, Antonio Cangiano wrote:

a.scan /[-+]?[0-9]*\,?[0-9]+/

Or to be less verbose you can use \d in place of [0-9] :slight_smile:

12

Will that expression include both integers and decimal numbers?

13

Let me see if I got it right then. I'll like to use periods only for my
decimal numbers. I also need normal integers so 24. being accepted won't
matter. Will this fix the problems you presented?:
/[-+]?(\d+\.?\d*)(?=\s|$)/

I don't know if it takes care of the last problem, because I didn't
understand it.

···

2006/2/12, Alexis Reigel <mail@koffeinfrei.org>:

>
> This should handle periods or commas as the separator.
>
> a = "24,4 + 55,2 + 55 - 44,0"
> => "24,4 + 55,2 + 55 - 44,0"
> a.scan /(\d+,?.?\d*)(?=\s|$)/
> => [["24,4"], ["55,2"], ["55"], ["44,0"]]
>

Some problems here:
- signs are disregarded ("-24,4" becomes "24,4")
- Invalid numbers are accepted: eg. "24,.4" "24,." "24." "24,"
- "." should be escaped. As you used it here, it means "any character"
(except newline), so many invalid numbers are accepted (e.g. "24w"...)
- If something different from whitespace follows the number, it is not
or false accepted, e.g. "24.4." becomes "4." instead of "24.4"
- ...

Alexis.

14

Seems I accidently got my text marked as a qoute in my last mail, so I'll
just send it a again:

Let me see if I got it right then. I'll like to use periods only for my
decimal numbers. I also need normal integers so 24. being accepted won't
matter. Will this fix the problems you presented?:
/[-+]?(\d+\.?\d*)(?=\s|$)/

I don't know if it takes care of the last problem, because I didn't
understand it.

···

2006/2/12, Jeppe Jakobsen <jeppe88@gmail.com>:

2006/2/12, Alexis Reigel <mail@koffeinfrei.org>:
>
> >
> > This should handle periods or commas as the separator.
> >
> > a = "24,4 + 55,2 + 55 - 44,0"
> > => "24,4 + 55,2 + 55 - 44,0"
> > a.scan /(\d+,?.?\d*)(?=\s|$)/
> > => [["24,4"], ["55,2"], ["55"], ["44,0"]]
> >
>
> Some problems here:
> - signs are disregarded ("-24,4" becomes "24,4")
> - Invalid numbers are accepted: eg. "24,.4" "24,." "24." "24,"
> - "." should be escaped. As you used it here, it means "any character"
> (except newline), so many invalid numbers are accepted (e.g. "24w"...)
> - If something different from whitespace follows the number, it is not
> or false accepted, e.g. "24.4." becomes "4." instead of "24.4"
> - ...
>
>
> Alexis.

15

Hi!

Will that expression include both integers and decimal numbers?

[-+]?([1-9]\d*(\,[0-9]+)?)|(0(\,[0-9]+)?)

has two parts:

[-+]?
([1-9]\d*(\,[0-9]+)?)|(0(\,[0-9]+)?)

The first one is an optional sign. The second one is an alternative
between to two cases:

[1-9]\d*(\,[0-9]+)?
0(\,[0-9]+)?

Let's first consider the first case

[1-9]\d*(\,[0-9]+)?

It has two parts, namely

[1-9]\d*
(\,[0-9])?

The first part by itself covers all integers larger than zero. The
overall expression additionally covers all floating point numbers
larger than 1.

Now the second case

0(\,[0-9]+)?

This one covers zero and all decimal numbers larger than 0 and smaller
than 1.

The regex I provided intentionally supports none of

[+-],\d+
[+-]0+\d+

You may as well use the shorter version

[-+]?(([1-9]\d*(\,\d+)?)|(0(\,\d+)?))

Wait a moment, I am not sure if that is correct. To be on the safe
side I'd rather use one of these where anything that follows the
optional sign has been put into another pair of parentheses:

[-+]?(([1-9]\d*(\,[0-9]+)?)|(0(\,[0-9]+)?))
[-+]?((([1-9]\d*(\,\d+)?)|(0(\,\d+)?)))

I am one of those guys who sometime run out of placeholders when doing
search and replace in vim (which has nine of them).

Josef 'Jupp' Schugt

···

At Sun, 12 Feb 2006 08:12:47 +0900, Jeppe Jakobsen wrote:
--
Let the origin be the middle of the earth, p(x,r) be the probability
density for finding person x at distance r. Make sure that a permanent
solution of int_0^R p(x,r) dr < 1 exists for R being the instantanous
value of the distance between earth and mars.

16

Well, that's what I get for dashing off a quick e-mail before dinner.
The last problem Alexis mentioned is caused by the overly-specific
lookahead at the end. Here's a version that fixes that:

irb(main):013:0> a = '24.5 + 24 + 24. + 24.4.'
=> "24.5 + 24 + 24. + 24.4."
irb(main):014:0> a.scan /[-+]?(\d+(?:\.\d+)?)(?=[^\d])/
=> [["24.5"], ["24"], ["24"], ["24.4"]]
irb(main):015:0>

One of the characters '-' or '+', optionally
Followed by at least one digit.
Followed by an optional group containing a period, and one or more digits.
The capturing group ends when the next character is something other
than a digit.

The (?:slight_smile: mess is there so that '24.' doesn't end up with the period on the end.

···

On 2/11/06, Jeppe Jakobsen <jeppe88@gmail.com> wrote:

Seems I accidently got my text marked as a qoute in my last mail, so I'll
just send it a again:

Let me see if I got it right then. I'll like to use periods only for my
decimal numbers. I also need normal integers so 24. being accepted won't
matter. Will this fix the problems you presented?:
/[-+]?(\d+\.?\d*)(?=\s|$)/

I don't know if it takes care of the last problem, because I didn't
understand it.

2006/2/12, Jeppe Jakobsen <jeppe88@gmail.com>:
>
> 2006/2/12, Alexis Reigel <mail@koffeinfrei.org>:
> >
> > >
> > > This should handle periods or commas as the separator.
> > >
> > > a = "24,4 + 55,2 + 55 - 44,0"
> > > => "24,4 + 55,2 + 55 - 44,0"
> > > a.scan /(\d+,?.?\d*)(?=\s|$)/
> > > => [["24,4"], ["55,2"], ["55"], ["44,0"]]
> > >
> >
> > Some problems here:
> > - signs are disregarded ("-24,4" becomes "24,4")
> > - Invalid numbers are accepted: eg. "24,.4" "24,." "24." "24,"
> > - "." should be escaped. As you used it here, it means "any character"
> > (except newline), so many invalid numbers are accepted (e.g. "24w"...)
> > - If something different from whitespace follows the number, it is not
> > or false accepted, e.g. "24.4." becomes "4." instead of "24.4"
> > - ...
> >
> >
> > Alexis.
>
>

17

Thank you for clearing things, up for me, but could you explain what the
last part of the expression Wilson provided me with means?

it's (?=[^\d])

···

2006/2/13, Josef 'Jupp' SCHUGT <jupp@gmx.de>:

Hi!

At Sun, 12 Feb 2006 08:12:47 +0900, Jeppe Jakobsen wrote:
>
> Will that expression include both integers and decimal numbers?

[-+]?([1-9]\d*(\,[0-9]+)?)|(0(\,[0-9]+)?)

has two parts:

[-+]?
([1-9]\d*(\,[0-9]+)?)|(0(\,[0-9]+)?)

The first one is an optional sign. The second one is an alternative
between to two cases:

[1-9]\d*(\,[0-9]+)?
0(\,[0-9]+)?

Let's first consider the first case

[1-9]\d*(\,[0-9]+)?

It has two parts, namely

[1-9]\d*
(\,[0-9])?

The first part by itself covers all integers larger than zero. The
overall expression additionally covers all floating point numbers
larger than 1.

Now the second case

0(\,[0-9]+)?

This one covers zero and all decimal numbers larger than 0 and smaller
than 1.

The regex I provided intentionally supports none of

[+-],\d+
[+-]0+\d+

You may as well use the shorter version

[-+]?(([1-9]\d*(\,\d+)?)|(0(\,\d+)?))

Wait a moment, I am not sure if that is correct. To be on the safe
side I'd rather use one of these where anything that follows the
optional sign has been put into another pair of parentheses:

[-+]?(([1-9]\d*(\,[0-9]+)?)|(0(\,[0-9]+)?))
[-+]?((([1-9]\d*(\,\d+)?)|(0(\,\d+)?)))

I am one of those guys who sometime run out of placeholders when doing
search and replace in vim (which has nine of them).

Josef 'Jupp' Schugt
--
Let the origin be the middle of the earth, p(x,r) be the probability
density for finding person x at distance r. Make sure that a permanent
solution of int_0^R p(x,r) dr < 1 exists for R being the instantanous
value of the distance between earth and mars.

--
"winners never quit, quitters never win"

18

Yes that worked, but I intend to convert the digits of my array to floats,
and I get a NoMethodError on to_f now when I do this:

digits[0] = digits[0].to_f

I don't understand that :-/

···

2006/2/12, Wilson Bilkovich <wilsonb@gmail.com>:

Well, that's what I get for dashing off a quick e-mail before dinner.
The last problem Alexis mentioned is caused by the overly-specific
lookahead at the end. Here's a version that fixes that:

irb(main):013:0> a = '24.5 + 24 + 24. + 24.4.'
=> "24.5 + 24 + 24. + 24.4."
irb(main):014:0> a.scan /[-+]?(\d+(?:\.\d+)?)(?=[^\d])/
=> [["24.5"], ["24"], ["24"], ["24.4"]]
irb(main):015:0>

One of the characters '-' or '+', optionally
Followed by at least one digit.
Followed by an optional group containing a period, and one or more digits.
The capturing group ends when the next character is something other
than a digit.

The (?:slight_smile: mess is there so that '24.' doesn't end up with the period on the
end.

On 2/11/06, Jeppe Jakobsen <jeppe88@gmail.com> wrote:
> Seems I accidently got my text marked as a qoute in my last mail, so
I'll
> just send it a again:
>
> Let me see if I got it right then. I'll like to use periods only for my
> decimal numbers. I also need normal integers so 24. being accepted won't
> matter. Will this fix the problems you presented?:
> /[-+]?(\d+\.?\d*)(?=\s|$)/
>
>
> I don't know if it takes care of the last problem, because I didn't
> understand it.
>
>
> 2006/2/12, Jeppe Jakobsen <jeppe88@gmail.com>:
> >
> > 2006/2/12, Alexis Reigel <mail@koffeinfrei.org>:
> > >
> > > >
> > > > This should handle periods or commas as the separator.
> > > >
> > > > a = "24,4 + 55,2 + 55 - 44,0"
> > > > => "24,4 + 55,2 + 55 - 44,0"
> > > > a.scan /(\d+,?.?\d*)(?=\s|$)/
> > > > => [["24,4"], ["55,2"], ["55"], ["44,0"]]
> > > >
> > >
> > > Some problems here:
> > > - signs are disregarded ("-24,4" becomes "24,4")
> > > - Invalid numbers are accepted: eg. "24,.4" "24,." "24." "24,"
> > > - "." should be escaped. As you used it here, it means "any
character"
> > > (except newline), so many invalid numbers are accepted (e.g.
"24w"...)
> > > - If something different from whitespace follows the number, it is
not
> > > or false accepted, e.g. "24.4." becomes "4." instead of "24.4"
> > > - ...
> > >
> > >
> > > Alexis.
> >
> >
>
>

--
"winners never quit, quitters never win"

19

Dňa Utorok 14 Február 2006 19:07 Jeppe Jakobsen napísal:

Thank you for clearing things, up for me, but could you explain what the
last part of the expression Wilson provided me with means?

it's (?=[^\d])

That's a positive zero-width lookahead. I think. Gotta love regexspeak.

In English: look for a single character that's not a decimal digit, and don't
include it in the match.

David Vallner

20

The scan process returns an array of arrays, so:
digits[0] is an Array containing '24.4'.
You could do:
digits.flatten!
just before digits[0], and get what you expect.

···

On 2/12/06, Jeppe Jakobsen <jeppe88@gmail.com> wrote:

Yes that worked, but I intend to convert the digits of my array to floats,
and I get a NoMethodError on to_f now when I do this:

digits[0] = digits[0].to_f

I don't understand that :-/

2006/2/12, Wilson Bilkovich <wilsonb@gmail.com>:
>
> Well, that's what I get for dashing off a quick e-mail before dinner.
> The last problem Alexis mentioned is caused by the overly-specific
> lookahead at the end. Here's a version that fixes that:
>
> irb(main):013:0> a = '24.5 + 24 + 24. + 24.4.'
> => "24.5 + 24 + 24. + 24.4."
> irb(main):014:0> a.scan /[-+]?(\d+(?:\.\d+)?)(?=[^\d])/
> => [["24.5"], ["24"], ["24"], ["24.4"]]
> irb(main):015:0>
>
> One of the characters '-' or '+', optionally
> Followed by at least one digit.
> Followed by an optional group containing a period, and one or more digits.
> The capturing group ends when the next character is something other
> than a digit.
>
> The (?:slight_smile: mess is there so that '24.' doesn't end up with the period on the
> end.
>
> On 2/11/06, Jeppe Jakobsen <jeppe88@gmail.com> wrote:
> > Seems I accidently got my text marked as a qoute in my last mail, so
> I'll
> > just send it a again:
> >
> > Let me see if I got it right then. I'll like to use periods only for my
> > decimal numbers. I also need normal integers so 24. being accepted won't
> > matter. Will this fix the problems you presented?:
> > /[-+]?(\d+\.?\d*)(?=\s|$)/
> >
> >
> > I don't know if it takes care of the last problem, because I didn't
> > understand it.
> >
> >
> > 2006/2/12, Jeppe Jakobsen <jeppe88@gmail.com>:
> > >
> > > 2006/2/12, Alexis Reigel <mail@koffeinfrei.org>:
> > > >
> > > > >
> > > > > This should handle periods or commas as the separator.
> > > > >
> > > > > a = "24,4 + 55,2 + 55 - 44,0"
> > > > > => "24,4 + 55,2 + 55 - 44,0"
> > > > > a.scan /(\d+,?.?\d*)(?=\s|$)/
> > > > > => [["24,4"], ["55,2"], ["55"], ["44,0"]]
> > > > >
> > > >
> > > > Some problems here:
> > > > - signs are disregarded ("-24,4" becomes "24,4")
> > > > - Invalid numbers are accepted: eg. "24,.4" "24,." "24." "24,"
> > > > - "." should be escaped. As you used it here, it means "any
> character"
> > > > (except newline), so many invalid numbers are accepted (e.g.
> "24w"...)
> > > > - If something different from whitespace follows the number, it is
> not
> > > > or false accepted, e.g. "24.4." becomes "4." instead of "24.4"
> > > > - ...
> > > >
> > > >
> > > > Alexis.
> > >
> > >
> >
> >
>
>

--
"winners never quit, quitters never win"