Change filename: def.y to def.yy
def.y ->def.tab.c , def.tab.h
def.yy->def.tab.cc, def.tab.hh

change Makefile:
def.y   def.tab.c ,
  |         |
  V         V
def.yy  def.tab.cc,
new variable: CPP=g++
change CC -> CPP in two places:
  def.tab.cc compilation
  whole program compilation 
  
add some code at begin of this file def.yy:
extern "C" int yylex();
extern "C" int yyerror(const char *msg, ...);
using namespace std;

change function parameters at two places of *.l:
int yyerror(const char *msg, ...);
int yyerror(const char *msg, ...){