- More questions about operator overloading - 2 Updates
- Fixing some undefined behavior - 1 Update
- More questions about operator overloading - 1 Update
| jacobnavia <jacob@jacob.remcomp.fr>: Jul 05 08:54PM +0200 Hi When doing operator overloading for some new type of number, there is a LOT of overloads to be done, one for each operator you want to overload, but also for each operation twice... For instance: T operator +(T arg1, double arg2); Then you handle T t; t = t+2.9; OK, but what about T operator +(double arg1, T arg2); That handles 2.9+t. Is that really necessary? Isn't addition commutative? No, since "abc" + "def" != "def" + "abc" That is why I have refrained in my implementation of operator overloading to make such an assumption. BUT Could it ever be that A != B and !(A == B) differ? I have decided no, so you do NOT have to overload != if you overload ==. Is that right? What do you think? Thanks in advance for your input. jacob |
| Ian Collins <ian-news@hotmail.com>: Jul 06 08:34AM +1200 On 06/07/2020 06:54, jacobnavia wrote: > I have decided no, so you do NOT have to overload != if you overload ==. > Is that right? > What do you think? Most implementations I've seen of operator != are simply "return !operator ==" Maybe you should consider the spaceship operator? -- Ian. |
| woodbrian77@gmail.com: Jul 05 12:57PM -0700 Shalom I have some undefined behavior in this program: https://github.com/Ebenezer-group/onwards/blob/master/src/cmw/tiers/cmwA.cc Basically I'm relying on some values being set after using placement new: req = &*pendingRequests.emplace_back(::new cmwRequest); frntBuf.getPacket((::sockaddr*)&req->frnt, &req->frntLn); gotAddr = true; ::new (req) cmwRequest(frntBuf); I need to be able to use "frnt" and "frntLn" after that last line. I guess the easiest way to handle it would be to pass the "frnt" and "frntLn" fields to the constructor I use with placement new. And then use them to initialize the fields. Thanks in advance. Brian Ebenenezer Enterprises - Enjoying programming again. https://webEbenezer.net |
| ram@zedat.fu-berlin.de (Stefan Ram): Jul 05 07:55PM >but also for each operation twice... >For instance: >T operator +(T arg1, double arg2); You can also do overloading combined with implicit type conversion: main.cpp #include <iostream> #include <ostream> class my_type { double x; public: my_type( double const x = 0.0 ): x{ x } {} // converting constructor my_type & operator +=( const my_type & o ){ x += o.x; return *this; } ::std::ostream & print( ::std::ostream & stream )const { return stream << x; }}; inline my_type operator +( my_type result, my_type const & other ) { result += other; return result; } inline ::std::ostream& operator << ( ::std::ostream & stream, my_type const & object ) { return object.print( stream ); } int main() { auto const c = my_type{ 1.0 }; auto const d = c + 2.0; ::std::cout << d << '\n'; } transcript 3 . That's the reason why we do not want to have the operator + as a member function. Type conversion should work on either operand! But sometimes explicit conversions are prefered. In this case, one might have to write c + my_type{ 2.0 } , but this could even be praised as being more clear. |
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