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Page: 1 2 3 4 5 6 7 8 9 10 11 12
Comments:
<0> cause your returning a value
<0> ah ic
<0> you have to do somehting different for the ***ignment
<1> ?
<1> god these compiler errors is annoying
<1> are
<2> how can i transform a string to a int?
<2> for example.. transform "12" to 12 ..
<0> corstan, your logic is messed up
<1> atoi("12")
<2> okay, thanks
<1> Twister2, I guess the lecturer's is
<1> but that can't help me now
<0> if you are trying to return a reference, then you have to return something referencable
<1> Twister2, take a look at these codes
<0> retrun 2.5; does not fly
<1> and try to compile them and link'em
<1> wait..
<2> test.cc:27: error: cannot convert `std::basic_string<char, std::char_traits<char>, std::allocator<char> >' to `const char*' for argument `1' to `int atoi(const char*)'
<3> std::stringstream cvt("12"); int x; cvt >> x; // x is now 12
<3> Use that.
<3> #include <sstream>
<3> More generally...
<3> std::stringstream cvt; cvt << "12"; int x; cvt >> x;
<3> Or, what you seem to be doing...
<2> :D.. isnt there a function to do that? :D
<3> std::string foo = "12"; std::stringstream cvt; cvt << foo; int x; cvt >> x;
<1> Twister2,
<3> That function isn't as extensible or as flexible as std::stringstream
<1> MyVector.cpp: http://www.noidea128.org/sourcefiles/15818.html
<3> Obviously, you're having trouble with it.
<3> atoi can only convert a const char* to an integer.
<3> std::stringstream can convert anything to anything else.
<3> That's a big win.
<1> Twister2, MyVector.h: http://www.noidea128.org/sourcefiles/15819.html
<3> If there's an overloaded operator>> and operator<< for a type, std::stringstream can use it.
<3> atoi knows not of such things.
<1> then main.cpp: http://www.noidea128.org/sourcefiles/15820.html
<1> try building
<1> and tell me
<1> anything Twister2 +
<0> u have 2 identical prototypes
<0> MyVector &MyVector::operator()(int i) { /*modify index i */ return this; }
<0> that would be my initial thought
<0> err, well thats not correct either
<0> it might be something like this:
<3> I hope someone has pointed out that it should be operator[]
<3> operator() has another purpose.
<1> Solamente, we had that discussion :)
<0> yeah, thats basically what is confusing the hell out of me
<3> And your reason for using () is?
<1> Solamente, a Matlab feature :) (no flaming)
<3> That's pretty dumb. This isn't Matlab.
<1> Twister2, what were you saying?
<0> it would be: double &MyVector::operator()(int i) { return A[i]; } or something like that.
<0> but as Solamente stated, normally it is the [] operator
<1> for doing something like: a = v(i) ?
<3> a = v[i];
<0> its a = v[i]
<3> [] is the index operator
<1> yes, I know
<0> () is function object operator
<1> but I have to confine myself to the task specification
<1> bear with me
<3> I'd only recommend () for a Matrix type, where a = matrix(x,y); makes more sense
<3> It's a nutty specification
<0> well, anyways, did you try the above?
<1> Solamente, this syntax is extended to what you are refering to, matrices later
<1> Twister2, I have already this:
<0> before the return, you should check bounds though
<1> / a = v(i)
<1> 51: double MyVector::operator() (int i)
<1> 52: const
<1> 53: {
<1> 54: return A[i];
<1> 55: }
<1> that is for extracting values from a vector
<1> but I need to figure out how to a body for:
<1> double &operator() (int i); // v(i) = a;
<0> I just told you it
<1> iaw, ***igning new values to the vector
<1> ok
<0> you need a const version too though I think
<1> talking about what I pasted ?
<0> and you have to bounds check...
<1> there's a const there
<0> Your totally missing the entire point of a vector cl*** by ignoring bounds
<0> unless you want () to be unsafe index
<1> this is merely an exercise in learning cl***es and header files
<1> I'll ignore out of bounds stuff
<0> I meant you need double const &MyVector::operator() (int i) const { } too
<4> Twister2: Why?
<0> I dunno
<0> :)
<4> Returning a reference lets you do lhs stuff. I'm not sure what returning a const reference would give you
<1> ok, anyways I see that whenever I am dealing with &operator() in a cl***
<5> it would only give you the ability to take it's address
<1> I just do: double &MyVector::operator() ...
<0> well, the const one should be public
<0> I think
<4> corstan: & doesn't deal with the operator. & deals with the double.
<3> Twister2: [] doesn't do bounds checking, for efficiency.
<3> What corstan is doing, however, should probably do bounds checking.
<1> what is exactly happening here:
<0> actually.. I just totalyl confused myself
<1> double &MyVector::operator()(int i)
<1> {
<1> return A[i];
<1> }
<1> I am returning the address of an entry in A?
<3> No.
<3> You're returning a reference.
<1> sorry, what I meant, the '&'
<3> But it's not going to work.
<1> Solamente, it is... :)
<1> it does
<3> What is A?
<1> a data member of cl*** MyVector
<3> I don't want to ask what MyVector is.
<1> another basic question:
<1> what's the point of putting 'const' here:
<1> double MyVector::operator() (int i) const {....}
<1> ?
<1> and also in the prototype in the h-file
<0> its just saying the member will not modify the object
<1> you mean the operator overloading function?
<0> meaning that v(i) <=== v will not be modified.
<3> Which is clearly incorrect if you're returning a non-const reference.
<0> no, thats for the other prototype
<3> Okay.
<0> and yeah, returning a const reference might be needed for some situation I suppsoe
<3> No, a copy is fine.
<0> ok
<5> sometimes you want to be able to do, double* d = &matrix(0, 1); though a different approach to that should be considered first
<3> You have. You just didn't realize it.
<1> Solamente, talking to me?
<3> Of course.
<1> heh
<3> Any time you're p***ing a parameter by reference to a function, and the function should not modify it, the parameter should be const.
<3> If you're not, you're tempting the devil.
<1> ok
<1> but what about const functions
<3> Likewise if the parameter is not a trivial type, but has value semantics.
<1> any similar examples there?
<3> It should be a const reference.
<3> Any time the method does not change the state of the object, it should be const.
<6> i am trying to change the caption of a button in vc++ what is teh correct command buttonname->??
<3> That way it can be used on const instances of the type.
<3> vERYbIGnOSE: SetWindowText, and that's not really a C++ question.
<6> ok thanks
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