Can Someone Translate this text

develop a program that outputs the user's weight on different planets. However, write the program using a class to represent the planet and its gravity. The class should include a constructor that allows a planet to be specified with a string, using any capitalization (if the string is not a planet name, then Earth should be assumed). The default construtor for the class will create an object representing Earth. The class has an observer operator that takes a weight on Earth as an argument and returns the weight on the planet. It should have a seond observer that returns the name of the planet as a string with proper capitalization.

I believe I can do this program, if only I understood what it is asking me to do specifically. Thank you in advance to whoever contribute their time into reading and replying to this message.

homework, i'll do it for a few quid..

plan it on paper then use your editor and compile it bit by bit. if you get any errors when u compile, rethink it on paper.

I know what the answer is, but I know more C than C++ so the final program would do you no good lol!

Which of these requirements don't you understand?

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develop a program that outputs the user's weight on different planets.

However, write the program using a class to represent the planet and its gravity.

The class should include a constructor that allows a planet to be specified with a string, using any capitalization (if the string is not a planet name, then Earth should be assumed).

The default construtor for the class will create an object representing Earth.

The class has an observer operator that takes a weight on Earth as an argument and returns the weight on the planet.

It should have a seond observer that returns the name of the planet as a string with proper capitalization.

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Do you know how to make a class?

Do you know how to make a constructor? Multiple (overloaded) constructors? A default constructor?

Do you know how to test a string to see if it's a planet name? Do you know how to re-capitalize a string?

Have you been given the relative gravational-pulls of each planet? (...Probably not too hard to find.)

I don't know what "observer operator" means, but it sounds like a type of member function. Do you know how to write member functions?

I claim - and Google agrees with me - that there is no such thing as an observer operator in C++ programming.

BTW, do you have to do it in C++? The introduction to typesafe enums in the Java5 documentation contains most of the code such a program would need in Java.

here is my header file. I believe I am missing something or doing something wrong here. no matter how I try to change it. I cannot compile it.

Code:

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class planet
{
public:
void getweight();
void print() const;

planet(string myplanet);
planet();

private:
string plan;
int weight;
float newweight;
};

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I just like to know why I cannot declare declare plan a string. Also, what is wrong with declaring the function name planet(string myplanet)?
Also I would like to know what "Multiple (overloaded) constructors" are, how to use it, and why is it relavent to this program. I have never heard of this type of constructor. I do know the gravitational pull of each planet and I know how to output the user's weight on each planet given the planet name and the user's weight. But I do not know how to re-capitalize a string. Oh yeah, and I am doing this in C++

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I just like to know why I cannot declare declare plan a string.

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You did. Who told you it's wrong ? Post his comments.
( Or more likely, your compilers error message. )

I do not understand why my compiler tells me that planet has not been declared when it has in my header file.

Code:

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planet::planet()
{
weight = myweight;
plan = myplanet;
}

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Here's how I define my class, can someone point out what is wrong with it. Maybe my logic is messed up, or maybe something is wrong with the way I define my function. Well, here it is

Code:

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#include "planet.h"
#include <iostream>

using namespace std;

void planet::getweight()
{
if(plan == "Mercury") {
newweight = weight * 0.4155;
}
if(plan == "Venus") {
newweight == weight * 0.8975;
}
if(plan == "Earth") {
newweight == weight * 1.0;
}
if(plan == "Moon") {
newweight == weight * 0.166;
}
if(plan == "Mars") {
newweight == weight * 0.3507;
}
if(plan == "Jupiter") {
newweight == weight * 2.5374;
}
if(plan == "Saturn") {
newweight == weight * 1.0677;
}
if(plan == "Uranus") {
newweight == weight * 0.8997;
}
if(plan == "Neptune") {
newweight == weight * 1.1794;
}
if(plan == "Pluto") {
newweight == weight * 0.0899;
}
}
void planet::Print() const
{
cout << newweight << endl;
}
planet::planet(string myplanet)
{
if(myplanet == "Mercury" || myplanet == "mercury") {
return "Mercury";
}
if(myplanet == "Venus" || myplanet == "venus") {
return "Venus";
}
if(myplanet == "Earth" || myplanet == "earth") {
return "Earth";
}
if(myplanet == "Moon" || myplanet == "moon") {
return "Moon";
}
if(myplanet == "Mars" || myplanet == "mars") {
return "Mars";
}
if(myplanet == "Jupiter" || myplanet == "jupiter") {
return "Jupiter";
}
if(myplanet == "Saturn" || myplanet == "saturn") {
return "Saturn";
}
if(myplanet == "Uranus" || myplanet == "uranus") {
return "Uranus";
}
if(myplanet == "Neptune" || myplanet == "neptune") {
return "Neptune";
}
if(myplanet == "Pluto" || myplanet == "pluto") {
return "Pluto";
}
if(myplanet == "")
return "you need to type a planet name";
else
return "Earth";
}
planet::planet()
{
weight = myweight;
plan = myplanet;
}

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Hey all, I like to thank all of you for taking the time to reply to my thread. I really need the help, I wish I joined this community sooner. I been stuck on this program for a while now. I just do not understand what I am doing wrong. I created a class before call the time class. It worked out great, but that program only focused on intergers. I guess my biggest problem is dealing with strings and associating a string with a float number.

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I just do not understand what I am doing wrong.

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But someone else does, or you would not be here :D

Your compiler already parsed your files and found out what is wrong. I don't feel like doing work in my sparetime that a machine already did way faster and way more accurate than I ever could. So what did your compiler say ?

it's saying all these, but...it doesn't make any sense.

/Users/orbitgalaxy/Gravity/gravity.h:7: error: expected `)' before "myplanet"
/Users/orbitgalaxy/Gravity/main.cpp:46: error: return type specification for constructor invalid
/Users/orbitgalaxy/Gravity/main.cpp:46: error: prototype for `planet::planet(std::string)' does not match any in class `planet'
/Users/orbitgalaxy/Gravity/gravity.h:2: error: candidates are: planet::planet(const planet&)
/Users/orbitgalaxy/Gravity/gravity.h:8: error: planet::planet()
/Users/orbitgalaxy/Gravity/main.cpp:49: error: returning a value from a constructor
/Users/orbitgalaxy/Gravity/main.cpp:52: error: returning a value from a constructor
/Users/orbitgalaxy/Gravity/main.cpp:55: error: returning a value from a constructor
/Users/orbitgalaxy/Gravity/main.cpp:58: error: returning a value from a constructor
/Users/orbitgalaxy/Gravity/main.cpp:61: error: returning a value from a constructor
/Users/orbitgalaxy/Gravity/main.cpp:64: error: returning a value from a constructor
/Users/orbitgalaxy/Gravity/main.cpp:67: error: returning a value from a constructor
/Users/orbitgalaxy/Gravity/main.cpp:70: error: returning a value from a constructor
/Users/orbitgalaxy/Gravity/main.cpp:73: error: returning a value from a constructor
/Users/orbitgalaxy/Gravity/main.cpp:76: error: returning a value from a constructor
/Users/orbitgalaxy/Gravity/main.cpp:79: error: returning a value from a constructor
/Users/orbitgalaxy/Gravity/main.cpp:81: error: returning a value from a constructor

This assignment seem so simple. How is it that I am having a hard time with it.

The first thing you probably need to do is #include <string> in planet.h. Declare the member plan in class planet to be of type std::string rather than string (I won't go into reasons now, but it's rarely a good idea to have "using namespace std;" in a header file).

That won't fix all your problems, but will probably fix some of them.

Quote:

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Here's how I define my class, can someone point out what is wrong with it.

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Blimey O'Reilly, where to start?

Code:

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planet::planet()
{
weight = myweight;
plan = myplanet;
}

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This is a compile time error. I suspect you are attempting to assign default values to weight & plan (but strangely not to newweight?), but have gone somewhat astray. How can you expect the data members to be initialised correctly in this manner? You are trying to assign values to them using undeclared, uninitialised variables. Are you aware of what an initialiser list is?

Code:

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planet::planet(string myplanet)
{
if(myplanet == "Mercury" || myplanet == "mercury") {
return "Mercury";
}

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Another compile time error. Constructors cannot return values in the same manner as functions (as your compiler points out).

I could go on to detail other flaws (such as using the comparison operator instead of assigning to newweight in the getweight() function), but I can't be arsed to be honest. I think a better suggestion would be for you to go over the fundamentals of classes until you have a better understanding of what their purpose is and how to implement them. With a bit of perserverance, you'll look back on this effort and laugh / cringe. I know I did at my first efforts.

I'm sorry, but what is an initialiser list?

An initialiser list is the preferred method for assigning values to data members in class constructors. For example:

Code:

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// initialise members to zero / null
planet::planet() : weight(0), newweight(0){} // strings are default initialised to a null string

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or:

Code:

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// initialise members to supplied values
planet::planet(const std::string& p, int w, int n) : plan(p), weight(w), newweight(n){}

---

If you initialise data members in the body of a constructor, it means that they are first default constructed, then assigned to. An initialiser list is more efficient as they are both constructed and initialised at the same time. This method is mandatory if a data member is a constant.

Ahem,

Code:

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// initialise members to supplied values
planet::planet(const std::string& p, int w, float n) : plan(p), weight(w), newweight(n){}

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Hey guys and girls, I changed my program around a little, I just like to know if I'm going in the right direction from what is required above.

Code:

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// this is my header file
class planet
{
private:
                float weight;
                float newweight;
                string plan;
public:
        planet();
        planet(float initweight, float initnewweight);
        float Getweight () const;
        float Getnewweight () const;
        void Write() const;
};
// followed by my .cpp file
#include "gravity.h"
#include <iostream>
#include <string>

planet::planet()
{
        weight = 0;
        newweight = 0 ;
        plan = "Earth";
}
planet::planet(float initweight, float initnewweight)
{
        weight =  initweight;
        newweight = initnewweight;
        plan = initplanet;
}
planet::planet(string initplanet)
{
        plan = initplanet;
}

float planet::Getweight () const
{
        return weight;
}
float planet::Getnewweight () const
{
        return newweight;
}
void planet::Write () const
{
        cout << "your weight on " << plan << "is" << newweight << endl;
}
// followed by my client file
#include <iostream>
#include "gravity.h"

using namespace std;

int main()
{
        cout << "Please enter your weight" << endl;
        cin >> initweight;
        cout << "Please enter the planet you wish to know how much you weight on, if you were to enter an
        incorrect planet name it will be assumed that Earth was your choice" << endl;
        cin >> initplanet;
        initweight.planet();
        initweight.Getweight();
        initweight.Write();
        return 0;
}

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currently, I only wanted to check one thing, and that's calling the function. Apparently, I just don't know how. :(

I broke it down to eight errors

Code:

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/Users/orbitgalaxy/scrap/gravity.h:6: error: 'string' does not name a type
/Users/orbitgalaxy/scrap/main.cpp:9: error: 'plan' was not declared in this scope
/Users/orbitgalaxy/scrap/main.cpp:15: error: 'plan' was not declared in this scope
/Users/orbitgalaxy/scrap/main.cpp:15: error: 'initplanet' was not declared in this scope
/Users/orbitgalaxy/scrap/main.cpp: At global scope:
/Users/orbitgalaxy/scrap/main.cpp:17: error: expected `)' before "initplanet"
/Users/orbitgalaxy/scrap/main.cpp:32: error: 'cout' was not declared in this scope
/Users/orbitgalaxy/scrap/main.cpp:32: error: 'plan' was not declared in this scope
/Users/orbitgalaxy/scrap/main.cpp:32: error: 'endl' was not declared in this scope

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going crazy because I'm just going around and around in circles, so I'm just going to start the program over in scratch again. Starting with a piece of blank white paper.
Thanks for the help ladies and gentlemen. Forums are great, but I would rather have your aim and program while chatting. Oh, and if there are any hint at all, that anyone could give me on my rough journey into pencil and paper programming. Please let me know. I'll be here 24.
Thanks all

Code:

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#include <string>

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include it to your .h file and see what happens..

also use this

Code:

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std::string plan;

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instead of

Code:

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string plan;

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Ok, forget every stupid thing I post, I figured it out. :) well most of it, yay. However, the one part i'm stuck on is creating a function that takes a weight on Earth as an argument and returns the weight on the planet.
Let's say the planet is Mercury with a gravitational pull of 0.4155. And Earth with a gravitational pull of 1.0. How would I associate the string Earth with the float 1.0? and how do I take a "weight on earth as an argument" when the user inputs the string "Earth"? This is the only code I am stuck on, and I would really appreciate anyone's help on this one. Thanks a whole lot.

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Originally Posted by CornedBee

I claim - and Google agrees with me - that there is no such thing as an observer operator in C++ programming.

BTW, do you have to do it in C++? The introduction to typesafe enums in the Java5 documentation contains most of the code such a program would need in Java.

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possibly they are supposed to overload an operator...or maybe they just have poor wording and are supposed to make a function that acts like an observer? heh

Sorry, but fyi, there are theoretically three categories of basic operations, and they are constructors, transformers, and "observers." The observer function allows programmers to observe the state of an instance of an Abstract Data Type without changing it. Try googling it again with these concepts. Thanks for all the help guys

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there are theoretically three categories of basic operations, and they are constructors, transformers, and "observers." The observer function allows programmers to observe the state of an instance of an Abstract Data Type without changing it.

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The thing is that the term 'operator' is not the same as the term 'function', so they should not be used interchangeably. That said, this "transformers/observers" concept sounds suspiciously like a "setters/getters" concept, and often setter and getter functions arent the best way of doing things.