Ruby trying to dynamically create unicode string throws "invalid Unicode escape" error

Question

I have a requirement wherein I want to dynamically create a unicode string using interpolation.For e.g. please see the following code tried out in irb

2.1.2 :016 > hex = 0x0905
 => 2309 
2.1.2 :017 > b = "\u#{hex}"
SyntaxError: (irb):17: invalid Unicode escape
b = "\u#{hex}"

The hex-code 0x0905 corresponds to unicode for independent vowel for DEVANAGARI LETTER A.

I am unable to figure how to achieve the desired result.

It seems you don't know how to format code block, which is a little surprising to see on a long-time user, please read the help and don't add your signature any more. — Yu Hao
– Yu Hao, Commented Nov 25, 2014 at 10:29

Stefan · Accepted Answer · 2014-11-25 12:39:27Z

5

You can pass an encoding to Integer#chr:

hex = 0x0905
hex.chr('UTF-8') #=> "अ"

The parameter can be omitted, if Encoding::default_internal is set to UTF-8:

$ ruby -E UTF-8:UTF-8 -e "p 0x0905.chr"
"अ"

You can also append codepoints to other strings:

'' << hex #=> "अ"

edited Nov 25, 2014 at 12:39

answered Nov 25, 2014 at 11:05

Stefan

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1 Comment

Jignesh Gohel Over a year ago

This answer seems more compact compared to Uri Agassi's answer. However both the techniques work smoothly. Thank you Uri and Stefan to both of you.

Uri Agassi · Accepted Answer · 2014-11-25 10:33:40Z

1

String interpolation happens after ruby decodes the escapes, so what you are trying to do is interpreted by ruby like an incomplete escape.

To create a unicode character from a number, you need to pack it:

hex = 0x0905
[hex].pack("U")
=> "अ"

answered Nov 25, 2014 at 10:33

Uri Agassi

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