testMacro.cc    :  simple preprocessor macros
absPitFall.cc   :  pitfall with macro computing abs value
testSelect.cc   :  conditional compilation

to compile:
c++ -Wall -o testMacro   testMacro.cc
c++ -Wall -o absPitFall  absPitFall.cc
c++ -Wall -o testSelect  testSelect.cc
c++ -Wall -D SELECTED=ALDO     -o testSelect1 testSelect.cc
c++ -Wall -D SELECTED=GIOVANNI -o testSelect2 testSelect.cc
c++ -Wall -D SELECTED=GIACOMO  -o testSelect3 testSelect.cc
