How can I parse a string of [fullwidth unicode integer characters](http://unicode.org/charts/PDF/UFF00.pdf) to an integer in ruby?

Attempting the obvious results in;

```
irb(main):011:0> a = "\uff11"
=> "１"
irb(main):012:0> Integer(a)
ArgumentError: invalid value for Integer: "\xEF\xBC\x91"
      from (irb):12:in `Integer'
      from (irb):12
      from /export/home/henry/apps/bin/irb:12:in `<main>'
irb(main):013:0> a.to_i
=> 0

```

The equivalent in python gives;

```
>>> a = u"\uff11"
>>> print a
１
>>> int(a)
1

```