From: Brian Candler <b.candler@...>
Date: 2008-11-03T22:43:06+09:00
Subject: Re: check if valid hexadecimal code?

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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