From: Benoit Daloze <eregontp@...>
Date: 2010-04-18T01:48:57+09:00
Subject: Re: what is String#ord?

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On 17 April 2010 18:41, Xavier Noria <fxn@hashref.com> wrote:

> On Sat, Apr 17, 2010 at 5:35 PM, Xavier Noria <fxn@hashref.com> wrote:
>
> > Ruby 1.9 docs for String#ord say:
> >
> >    Return the <code>Integer</code> ordinal of a one-character string.
> >
> > What does that mean? Check for example
> >
> >    "=D7".ord # =3D> 215
> >    "=D7".bytes.to_a # =3D> [195, 151]
>
> Trial and error suggests it is the code of the character in the
> encoding of the string:
>
>    euro =3D "\u20AC"
>
>    euro.ord.to_s(16) # =3D> "20ac"
>    euro.encode("iso-8859-15").ord.to_s(16) # =3D> "a4"
>
> That is what the source code suggests also:
>
> VALUE
> rb_str_ord(VALUE s)
> {
>    unsigned int c;
>
>    c =3D rb_enc_codepoint(RSTRING_PTR(s), RSTRING_END(s), STR_ENC_GET(s))=
;
>    return UINT2NUM(c);
> }
>
>
p "=D7".ord # =3D> 215
p "=D7".bytes.to_a # =3D> [195, 151]
p "=D7".encoding # =3D> #<Encoding:UTF-8>
p "=D7".codepoints.to_a #=3D> [215]

In UTF-8, (and Unicode in general), one byte is not always(or even never) a
character.
A codepoint represent a character ;)

So, you can think of ord as codepoints[0], and that number of course depend=
s
of the String's Encoding.

Regards,
B.D.

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