I have installed Ruby and the Ruby-doc package (and also some other doc
packages related to Ruby gems). However, ri does not work for core
packages. Example:


$ ri String
= String < Object

(from gem bigdecimal-1.3.2)
------------------------------------------------------------------------------
= Instance methods:

  to_d

(from gem rake-11.3.0)
------------------------------------------------------------------------------
= Instance methods:

  ext, pathmap, pathmap_explode, pathmap_partial, pathmap_replace

We can see that String related methods from the gems are displayed, but
not what is in the core package. Similarily:

$ ri 'String#length'
Nothing known about String#length

Is this a bug?