Short version: It installed fine, but one of the dependencies' for the
sexp gem documentation didn't compile correctly (the gem will still
work, just not the documentation).

Long version: The error you got has to do with documentation (rdoc)
generation.  The sexp gem installed fine, there was just an error in
the documentation generation for rparsec, a dependency for the sexp
gem.  The second time you tried to install it, gem didn't try to
redownload anything because it was already installed, and it didn't
regenerate the rdoc for anything except what you wanted to install.

I could be wrong, though.
~Andrew (@andrew12_ on Twitter)



On Tue, Sep 20, 2011 at 3:58 PM, amir e. <aef1370 / gmail.com> wrote:
> Hi
> When I tried to install 'sexp' gem for first time (with this statement :
> 'gem install sexp' ) ruby gives me an error but when for second time I
> tried with the same statement ruby didn't give me an error . Why ruby
> behave such this ?
>
> ** I take a picture from steps that I tried to install that gem **
>
> Attachments:
> http://www.ruby-forum.com/attachment/6614/Capture.PNG
>
>
> --
> Posted via http://www.ruby-forum.com/.
>
>