libzahl is a library for arbitrary size integers, bigint.
You can browse its source code repository or get a copy using git with the following command:
git clone https://git.suckless.org/libzahl
Apart from the man pages,
libzahl's repository also contains a
reference sheet and a
If you cannot find what you need in the man pages, the reference sheet, or the reference manual, the best way to get support is to contact the author via e-mail.