[Help-gnu-radius] Q bout gnu-radius installation

[Edie-Susatyo]

Dear sir,

My name edie and I was download gnu-radius 0.96.2 and try to
install it in our company's server. But i have problem when
i try to configure it.
I get error messages like this ...
---------------
checking for flex ... no
checking for lex ... no
./configure: flex: command not found
checking for flex ... lex
checking for yywrap in-ll ... no
checking lex output file root .. ./configure: lex: command
not found
configure error: cannot find output from lex; giving up
---------------
and i can't continue.

FYI, i'm not familiar with languange program. 
But, our company want to implement radius for our network.
So, please help me to solve that problem.
Give me further clues to install gnu-radius.
Thanks and i'm glad to hearing from you in the near future.

Edie Susatyo