Main.cc: In function ‘int main()’: Main.cc:13:30: error: ‘cnt’ was not declared in this scope if(double((d-b)/(a-c))==0) cnt=0.00001; ^~~ Main.cc:13:30: note: suggested alternative: ‘int’ if(double((d-b)/(a-c))==0) cnt=0.00001; ^~~ int