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check if valid hexadecimal code?

Chealsea S.

11/2/2008 9:31:00 PM

How would you check if a string is a valid hexadecimal code?
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5 Answers

Avdi Grimm

11/2/2008 9:57:00 PM

0

On Sun, Nov 2, 2008 at 4:30 PM, Chealsea S. <youngliars@gmail.com> wrote:
> How would you check if a string is a valid hexadecimal code?

irb(main):007:0> hex_pattern = /^[[:xdigit:]]+$/
=> /^[[:xdigit:]]+$/
irb(main):008:0> hex_pattern === "0123456789ABCDEF"
=> true
irb(main):009:0> hex_pattern === "Chunky Bacon"
=> false


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Craig Demyanovich

11/2/2008 10:03:00 PM

0

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

On Sun, Nov 2, 2008 at 5:56 PM, Avdi Grimm <avdi@avdi.org> wrote:

> On Sun, Nov 2, 2008 at 4:30 PM, Chealsea S. <youngliars@gmail.com> wrote:
> > How would you check if a string is a valid hexadecimal code?
>
> irb(main):007:0> hex_pattern = /^[[:xdigit:]]+$/
> => /^[[:xdigit:]]+$/
> irb(main):008:0> hex_pattern === "0123456789ABCDEF"
> => true
> irb(main):009:0> hex_pattern === "Chunky Bacon"
> => false


I wonder if you should use /\A[[:xdigit:]]+\z/ to match the beginning and
end of the string instead of the beginning and end of the line.

Another options is to use String#hex method and check the return value,
though I find it weird that it returns 0 on error, since "0x0".hex also
returns 0

Regards,
Craig

Chealsea S.

11/2/2008 11:17:00 PM

0

I tried "hex_pattern" with a string like "asdbgg" and it does not
produce an error, even though "g" isn't A-F 0-9.

I should specify that I'm trying to build a hexadecimal color checker.
I tried the folllowing code but it doesn't work:

def ishex(hexcolor)
if (hexcolor.to_s.length == 6) == false
then
false
elsif hexcolor.hex == 0
false
else
true
end
end



Thanks for any help.



Avdi Grimm wrote:
> On Sun, Nov 2, 2008 at 4:30 PM, Chealsea S. <youngliars@gmail.com>
> wrote:
>> How would you check if a string is a valid hexadecimal code?
>
> irb(main):007:0> hex_pattern = /^[[:xdigit:]]+$/
> => /^[[:xdigit:]]+$/
> irb(main):008:0> hex_pattern === "0123456789ABCDEF"
> => true
> irb(main):009:0> hex_pattern === "Chunky Bacon"
> => false
>
>
> --
> Avdi
>
> Home: http:...
> Developer Blog: http:.../devblog/
> Twitter: http://twitte...
> Journal: http://avdi.livej...

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Avdi Grimm

11/2/2008 11:23:00 PM

0

On Sun, Nov 2, 2008 at 6:17 PM, Chealsea S. <youngliars@gmail.com> wrote:
> I tried "hex_pattern" with a string like "asdbgg" and it does not
> produce an error, even though "g" isn't A-F 0-9.

irb(main):012:0> hex_pattern === "asdbggg"
=> false

I can't reproduce that behavior. What version/platform of Ruby are you on?

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Avdi

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Brian Candler

11/3/2008 1:43:00 PM

0

Craig Demyanovich wrote:
> Another options is to use String#hex method and check the return value,
> though I find it weird that it returns 0 on error, since "0x0".hex also
> returns 0

It just stops at the first non-hex character.

irb(main):002:0> "123zzz".hex
=> 291

But you could do this:

irb(main):003:0> str="123"
=> "123"
irb(main):004:0> Integer("0x#{str}")
=> 291
irb(main):005:0> str="123zzz"
=> "123zzz"
irb(main):006:0> Integer("0x#{str}")
ArgumentError: invalid value for Integer: "0x123zzz"
from (irb):6:in `Integer'
from (irb):6
from :0
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