Add another version slightly cleaned up and using flex/bison with a header file
-rw-r--r-- 62 .gitignore
-rw-r--r-- 417 Makefile
-rw-r--r-- 132 cal.l
-rw-r--r-- 606 cal.y
-rw-r--r-- 184 calc.l
-rw-r--r-- 600 calc.y
drwxr-xr-x - doc