u need find a copy of readline.tar.gz (e.g., ftp://ftp.gnu.org/gnu/readline/),
and untar it, then cd the readline source directory, ./configure, then make.
Warnings are OK to neglect, as far as you can get "libreadline.a" file.

You may want to save this "libreadline.a" file for future use, e.g.:
mkdir $HOME/bin
mv libreadline.a $HOME/bin

Then go back to ytin's source directory, do this:
./configure --libdir $HOME/bin
make

You may want to move the final "tt++" file to $HOME/bin and delete the readline
and yTin source files to save disk space.