c++ - Making prefix operator do nothing on certain circumstances -

overloading postfix operator doesn't work

here program yesterday after fixed it. having trouble negate prefix operator doing if hours , days set @ zero.

numdays numdays::operator--() {     --hour;     simplify();     return *this; }  numdays numdays::operator--(int) {     numdays obj1(*this);      if(day == 0 && hour > 0)         {   hour--; }      simplify();     return obj1; } 

if try use if state postfix operator, both of operators not work if day , hours not @ 0. how make prefix operator nothing if day , hour @ 0?

first, logic seems incorrect, pointed out wimmel. think want disable operator-- when both day,hour zero.

second, prefix operator should return reference.

third, may have postfix operator use prefix one, don't duplicate code.

all in all:

numdays& numdays::operator--() {     if (day > 0 || hour > 0)     {        --hour;        simplify();     }     return *this; }  numdays numdays::operator--(int) {     numdays copy(*this);     ++(*this);     return copy; }