right alt on macbook configuration

[Gergely Buday]

Hi there,

I tried to configure my right alt on my macbook not to behave as a
numeric enter but to behave as a right alt.

I tried putting this into .Xmodmap, following

http://www.edwardotis.net/tech/?p=224

$ cat .Xmodmap
keycode 66 = Alt_L
clear Mod1
add Mod1 = Alt_L Alt_R

and running

~$ xmodmap ~/.Xmodmap
X Error of failed request:  BadValue (integer parameter out of range
for operation)
  Major opcode of failed request:  118 (X_SetModifierMapping)
  Value in failed request:  0x17
  Serial number of failed request:  13
  Current serial number in output stream:  13

What am I doing wrong?

Also, I tried to look for this, following

http://ubuntuforums.org/showthread.php?t=1173264

---
Go to SYSTEM > PREFERENCES > KEYBOARD

Then choose the LAYOUTS tab.
There is a button down there called LAYOUT OPTIONS, click it!

Expand the KEY TO CHOOSE 3RD LEVEL options.
And select the option PRESS ENTER KEY ON KEYPAD TO CHOOSE 3RD LEVEL.
---

But this seems to be valid only on an old, 9.04 Ubuntu, I have 13.04.

How can I use my right alt as a right alt, i.e. Alt Gr?

- Gergely