Check if valid hexadecimal code?

Ruby
1

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

2

On Sun, Nov 2, 2008 at 4:30 PM, Chealsea S. [email protected]
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://avdi.org
Developer Blog: Avdi Grimm, Code Cleric
Twitter: http://twitter.com/avdi
Journal: http://avdi.livejournal.com

3

On Sun, Nov 2, 2008 at 5:56 PM, Avdi G. [email protected] wrote:

On Sun, Nov 2, 2008 at 4:30 PM, Chealsea S. [email protected] 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

4

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 G. wrote:

On Sun, Nov 2, 2008 at 4:30 PM, Chealsea S. [email protected]
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://avdi.org
Developer Blog: Avdi Grimm, Code Cleric
Twitter: http://twitter.com/avdi
Journal: http://avdi.livejournal.com

5

On Sun, Nov 2, 2008 at 6:17 PM, Chealsea S. [email protected]
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?

–
Avdi

Home: http://avdi.org
Developer Blog: Avdi Grimm, Code Cleric
Twitter: http://twitter.com/avdi
Journal: http://avdi.livejournal.com

6

Craig D. 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