The book Flex & Bison (IBAN 978-0-596-15597-1) released on August 2009 by O'Reilly written by John Levine contains a lot of code examples. On the preface, page xv, the book prints the following URL
ftp://ftp.iecc.com/pub/file/flexbison.zip
from which you can download the examples from this book. The link (as of Sep. 2019) is still online and you can still download the zip file.
Executing make does indeed compile many examples, however (I'm using GCC 8.3.0 on Gentoo Linux) most of them
compile with warnings and at some point it simply stops with a compile error. Inspecting the source code reveals
that many examples are simply outdated, specially the C code.
Wanting to refresh my knowledge about these two tools, I decided to go through the whole book again and rewrite the code examples one by one. I'll update the outdated C code and use C99 instead. I'll also try to fix any flex/bison code that does not compile with modern version of these tools. I'll be using flex-2.6.4 (the book uses flex-2.5.35) and bison-3.1 (the book uses bison-2.4.1).
I am neither the author of the book nor the author of the examples. I also don't own the copyright of the book. I simply bought a physical copy of this book.
I decided to put the revised versions on github because the original files are (still) publicly available.