Flex/Bison examples

Document: http://web.iitd.ac.in/~sumeet/flex__bison.pdf
I followed the samples in above doc, but modified a little to work with MAC.

Install Flex/Bison on MAC

  brew install bison
  brew install flex

Sample1

  cd sample1
  make
  ./a.out  

Then, type something and hit Enter, it will shows number of lines/words/chars as "wc" command.
<Ctrl-D> or <Ctrl-C> to quit

Sample2

  cd sample2
  make
  ./fb1-5.out 

Then, type 2 + 4 * 2 and hit Enter, it will show 10 as well as some debug info.