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C++ Help?
- Thread starter AcciDante
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cpp_is_king
Member
AcciDante said:
Well, just describe your actual problem instead of your proposed solution. We know your solution was something like "derive some classes here and there, make the Cat class implement a method called purr(), etc" But what was the original problem? What is your program trying to do?
Can anyone help me with this code?
There is more to the code than this but it all works as it should so I won't bother posting it. Just know I created a struct called data with members m_assignmentGrade and m_labGrade (both array's of float values).
I keep getting an error saying that average cannot be used as a function. The average function works as it should.
Any tips?
Code:
bool failed(data student, float &average)
{
float AssignmentAverage= average(student.m_assignmentGrade,12);
float LabAverage=average(student.m_labGrade,11);
if(AssignmentAverage<50||LabAverage<50||0.5*(student.m_midterm+student.m_final)<50)
{
return true;
}
average=0.2*student.m_midterm+0.3*student.m_final+0.2*LabAverage+0.3*AssignmentAverage;
return false;
}There is more to the code than this but it all works as it should so I won't bother posting it. Just know I created a struct called data with members m_assignmentGrade and m_labGrade (both array's of float values).
I keep getting an error saying that average cannot be used as a function. The average function works as it should.
Any tips?
nelkon and parker
Member
Quick guess... your argument name is average. Causing issues with the function name average.
cpp_is_king
Member
AcciDante said:
I know, but that still has nothing to do with your actual problem. What program are you trying to write? What is your program supposed to do?
Hey GAF, beginner here. Working on an assignment for class that deals with having to add, subtract, multiply, and divide fractions. The assignment calls for returning answers this way:
Example
lease enter a problem: 1/2 + 1/4
The answer is 3/4
Now my question is, how do I return the answer this way(fraction form)?
In the header file I have the following function
And in the main I have this:
Sorry if it's a little rough, trying to get it to work correctly before I start reducing and do the other functions, etc.
Example
lease enter a problem: 1/2 + 1/4The answer is 3/4
Now my question is, how do I return the answer this way(fraction form)?
In the header file I have the following function
Code:
int functionadd(int a, int b, int c, int d)
{
int num, den, sum;
num = (a * d) + (b * c);
den = (b * d);
sum=num/den;
return sum;
}And in the main I have this:
Code:
#include <iostream>
#include <string>
#include <cmath>
#include "homework_4_head.h"
using namespace std;
int main( )
{
int numa, dena, numb, denb, result; //variable declaration
char div; //dummy variable
char operat; //Operator
welcome();
cout<<" Enter your problem. "<<endl;
cin >> numa >> div >> dena >> operat >> numb >> div >> denb;
functionadd(numa, dena, numb, denb);
result=functionadd(numa, dena, numb, denb);
cout<<" The sum is "<<result<<endl;
return 0;
}Sorry if it's a little rough, trying to get it to work correctly before I start reducing and do the other functions, etc.
You can't just return an integer if that's the case. The most sensible way of doing this would be to define a class or structure representing a fraction. Something like this:Heysoos said:
Code:
class Fraction
{
public:
int numerator;
int denominator;
};Then have your function add return a Fraction object, rather than an integer. Then, once its out of your addition function, you can print it however you want.
Ok I'm back. Trying to reduce the fractions, but I think I'm doing it wrong.
Is there something wrong here? When I build it, it comes back with no errors, however, when I run it:
It does the same with the other functions. I think I'm doing the Euclid's algorithm wrong, but I'm not sure exactly what I'm doing wrong.
Trying to reduce the fractions, but I think I'm doing it wrong.
Code:
void functiondivide(int a, int b, int c, int d)
{
int num, den, remainder;
int dividend, divisor;
dividend = 0;
divisor = 0;
num = (a * d);
den = (b * c);
if(num>den)
{
num=dividend;
den=divisor;
}
else
{
den=dividend;
num=divisor;
}
do{
remainder = dividend % divisor;
if(remainder != 0)
{
dividend = divisor;
divisor = remainder;
}
}while(remainder =! 0);
num = (num / divisor) * divisor;
den = (den / divisor) * divisor;
cout<< " " << num << "/" << " " << den <<endl;
return;
}Is there something wrong here? When I build it, it comes back with no errors, however, when I run it:
It does the same with the other functions. I think I'm doing the Euclid's algorithm wrong, but I'm not sure exactly what I'm doing wrong.
CrayzeeCarl
Member
You're dividing by zero (divisor).Heysoos said:Ok I'm back.
Just at a quick glance, shouldn't this:
Code:
if(num>den)
{
num=dividend;
den=divisor;
}
else
{
den=dividend;
num=divisor;
}
Code:
if(num>den)
{
dividend=num;
divisor=den;
}
else
{
dividend=den;
divisor=num;
}
poweld said:
I LOVE YOU
I hadn't even noticed I had it set to =! 0. Changing it did the trick. ! Thank you so much. I went over the code over and over and still overlooked it. AcciDante said:
No. :/ Have yet to learn how to use it in the class. I'll see if I can learn how to use it myself slowly.
No problem, you'll get the hang of it.Heysoos said:I LOVE YOU
No. :/ Have yet to learn how to use it in the class. I'll see if I can learn how to use it myself slowly.
You should certainly learn how to use the debugger. It's dead simple (assuming you're using Visual Studio) and will help you greatly in zero-ing in on problems like this.
Zoe means using some statements that print debug lines to help you "see" what is happening in your program. For example, just putting std::cout << "test" << std::endl; at the end of your loop would tell you that your loop is exiting after the first run, and that there's clearly something wrong with your loop test.Heysoos said:What exactly do you mean by this?
Outputting debug information is extraordinarily helpful, especially as your programs become more complicated. Our code base, for example, likely exceeds a million lines. If we didn't have a huge amount of debug messages spread throughout the code, we engineers would have a very tough time even beginning to locate the source of bugs.
I have a programming related question. Not at all related to C++ but i guess all the real cool kids know C++ and seem to enjoy contributing to this thread and I don't want to create another thread for a specific question, so, on the other side of the spectrum, Java...
Anyone have any experience with Apache and JBoss? I have this problem at work which has been killing me and I would appreciate any help I can get.
Anyone have any experience with Apache and JBoss? I have this problem at work which has been killing me and I would appreciate any help I can get.
Right, I've got what I think is a simple problem but I just can't figure out how to sort it.
What I'm trying to do is go through a char array one element at a time and grab any numbers and place them into a second char array (the second array also needs to be a char array because I'm going to put other letters into it later). The problem is when I try to do this I'm constantly getting strange characters output to the screen, kind of like an inverted "d".
Here's what the code pretty much looks like:
I'm sure the issue is something to do with the "array2 = array1;" line because everything else I've tested many times over and they work on their own.
EDIT: Small extra, I think the number of gibberish symbols is the unassigned positions in the array or something, I'd like to get rid of the 30 size limit on the arrays, which works for array2, but for array1 I get an "incomplete type not allowed" error.
What I'm trying to do is go through a char array one element at a time and grab any numbers and place them into a second char array (the second array also needs to be a char array because I'm going to put other letters into it later). The problem is when I try to do this I'm constantly getting strange characters output to the screen, kind of like an inverted "d".
Here's what the code pretty much looks like:
Code:
Assume that array1 is already holding the value ch33se, in the positions 0-5.
class example
{
char array1[30];
char array2[30];
public:
void getNumbers()
for (int i = 0; array1[i] != '\0'; i++)
{
if (isdigit(array1[i]))
{
array2[i] = array1[i];
}
char* returnArray2()
{
return array2;
}
};
int main()
{
example x1;
x1.getNumbers();
cout << returnArray2();
return0;
}I'm sure the issue is something to do with the "array2 = array1;" line because everything else I've tested many times over and they work on their own.
EDIT: Small extra, I think the number of gibberish symbols is the unassigned positions in the array or something, I'd like to get rid of the 30 size limit on the arrays, which works for array2, but for array1 I get an "incomplete type not allowed" error.
cpp_is_king
Member
Colkate said:
Problem 1: array2 is not initialized, and thus you are trying to print a string without a null terminator at the end.
Solution 1: Add the following function to the class declaration:
Code:
example()
{
::memset(array2, 0, sizeof(array2));
}All that aside, this is honestly some fairly messy code, and there is almost certainly a better way to achieve what you're trying to accomplish, if you explain the problem at a higher level.
Problem 2: Since you are only copying the item into the other array if it is a digit, then this still will not work. The text in the first 6 characters, which you've said is ch33se begins with a letter, not a number. So the loop will copy nothing into positions 0 and 1, for example, nor into positions 3 and 4. What you end up with is something like this:
Array 1
c h 3 3 s e
Array 2
x x 3 3 x x
Here, I'm using x to represent a null terminator, not the letter x. In other words, nothing is in those positions.
Now, when you try to print array 2, it just stops because it encounters a null terminator immediately (after my modification anyway where you initialize the array to 0).
Solution 2: what you need to do is keep TWO SEPARATE COUNTERS. The position you are reading from, and the position you are writing from. What you want is for your array to end up like this:
Array 2
3 3 x x x x
Thus, the index that you write into cannot be the same as the index you read from.
Code:
void getNumbers()
{
int in=0;
int out=0;
while (array1[in] != '\0')
{
if (isdigit(array1[in]))
{
array2[out] = array1[in];
++out;
}
++in;
}
}Colkate said:
You need a second counter for the array2 offset, because here's what your code does is this:
Code:
array1[] = { 'c','h','3', '3', 's', 'e' }
array2[] = { '\0','\0','3','3','\0','\0'}
Code:
array1[] = { 'c','h','3', '3', 's', 'e' }
array2[] = { '3','3','\0','\0','\0','\0'}
Code:
void getNumbers()
{
int j=0;
for (int i = 0; array1[i] != '\0'; i++)
{
if (isdigit(array1[i]))
{
array2[j++] = array1[i];
}
}
}Got that all working now, I added in the second counter to determine the write location in the second array separate from the read location of the first array, which I can't believe I managed to mess up. Then added the function to initialize the second array which stopped the result displaying the empty array contents. Thanks for the help guys.
I know you fixed it, but what I'd use is strcat instead of keeping a second pointer. Array1 and Array2 while technically arrays, are the standard/basic string format of C++ and there are tons of functions built around the char*, char[] strings.
Just make sure you always initialize the strings using memset, ZeroMemory or just = {\0}
Just make sure you always initialize the strings using memset, ZeroMemory or just = {\0}
Zoramon089
Banned
Grr, why can't you be like Java C++
Anyway, I've got this class called point with a couple public methods
And this other class called Line which takes in points and uses it's x,y values to create the equation for the line
I keep geting an error on that last line saying expression must have (pointer-to- ) function type
Anyway, I've got this class called point with a couple public methods
Code:
class Point
{
public:
...
const int x()
{
return x; // private var
}
const int y()
{
return y; // private var
}And this other class called Line which takes in points and uses it's x,y values to create the equation for the line
Code:
class Line
{
public:
Line(Point p1, Point p2)
{
point1 = p1;
point2 = p2;
equation[0] = (point2.y()-point1.y())/(point2.x-point1.x());I keep geting an error on that last line saying expression must have (pointer-to- ) function type
CrayzeeCarl
Member
Why is p1 a pointer but p2 isn't? For pointers, you can't use the object.function() notation that way because the "." operator has precedence over the dereference operator (which you're also not dereferencing p1, btw). To call a method on a pointer, use "->" instead of ".". Also, you're not putting the parentheses after the "x" on point2.Zoramon089 said:
Another thing - you need to cast everything as doubles or your division won't work. Dividing an int by another int will drop the remainder and won't round. Adding 0.5 will round them.
If point1, point2, p1 and p2 should be pointers, do this:
Code:
class Line
{
public:
Line(Point *p1, Point *p2)
{
point1 = *p1;
point2 = *p2;
equation[0] = (double)(point2->y()-point1->y())/((double)(point2->x()-point1->x()) + 0.5;If you don't want pointers, do this:
Code:
class Line
{
public:
Line(Point p1, Point p2)
{
point1 = p1;
point2 = p2;
equation[0] = (double)(point2.y()-point1.y())/(double)(point2.x()-point1.x()) + 0.5;Elfforkusu
Member
Code:
class Line
{
public:
Line(const Point& p1, const Point& p2)
: point1(p1)
, point2(p2)
{
equation[0] = (point2.y()-point1.y())/(point2.x()-point1.x());
(of course, you'd have to change your "x()" and "y()" definitions to "x() const" and "y() const", but whatev)
Zoramon089
Banned
Err, p1 shouldn't be a pointer. That was just a typo I accidentally forgot to change when trying things out
cpp_is_king
Member
1) Don't make member functions with the same name as member variables. You have x() and x, this is ambiguous to the compiler.
2) You're writing point2.x, but you mean point2.x().
3) Why return const int? You're returning by value anyway, it's not like the receiver can modify the result.
Also, word of advice: Don't use encapsulation just to say you used it. If you have methods called getx() and setx() and all they do is return x; and x = param; then what's the point? Just expose them publicly in that case.
2) You're writing point2.x, but you mean point2.x().
3) Why return const int? You're returning by value anyway, it's not like the receiver can modify the result.
Also, word of advice: Don't use encapsulation just to say you used it. If you have methods called getx() and setx() and all they do is return x; and x = param; then what's the point? Just expose them publicly in that case.
cpp_is_king
Member
usea said:
That's what everyone says, when was the last time you did that? Give a specific example, please.
You become a good programmer once you learn which of the "good practices" you can break, and when.
To what end are you breaking this good practice? To save 20 seconds typing? Betting on the fact that nothing will change. You sound like you have an axe to grind because somebody got a bit overzealous in preaching SOLID or something. There are measurable, actual benefits for this good practice and no reason to avoid it.cpp_is_king said:
The benefits showed quickly when I started working with groups of people on software instead of just myself, and when the software I wrote lasted months instead of a weekly homework assignment.
The notion that you shouldn't bother to type out setters/getters because "what's the point?" is not a very well-reasoned one. When there's a dozen classes written by 3 different people that use those functions, you'll be glad they're there when requirements change.
I don't even do traditional business software or consulting, and I'm not really into the movements like agile. But even I can recognize the immense benefit.
cpp_is_king
Member
usea said:
To the person who originally asked the question about points: Sorry for derailing your question.
That being said, surely even you can realize what an immense overstatement that is? Immense benefits are things like LTCG or OOP in general. A freaking getter and setter is not an immense benefit.
It's a freaking point for christ's sake. I can pretty much guarantee you that if your get function is doing anything other than returning x in your extremely primitive point class, you have bigger problems to worry about.
But ok, I'll humor you for a second. Suppose you are making use of an external library that is optimized for, oh idk, SSE. It provides a function that transforms a 3 dimensional point by a transformation matrix. Since this is an external library and has no idea what your proprietary object hierarchy looks like, it simply exposes a function like this:
Transform(m11, m12, m13, m21, m22, m23, m31, m32, m33, *px, *py, *pz);
OOOOOPS.
"Aha!", you say. "You can simply provide a transform member function that has access to the internals of the class". Terrific. That is, of course, unless your code base is like every other code base in the world (i.e. imperfect). Oh *that* matrix. That one is in row-major order. Maybe I should make a TransformInRowMajor() function instead, or just add a bool to the end of my Transform() function that says which order to interpret the matrix in. (Hint: This is starting to get stupid). Maybe it's actually a 4x4 matrix but I only want to transform using the 3x3 matrix in the upper left corner. Sure would be nice if I could just access those pesky little x, y, and z variables.
Download any library in the world for doing 3D math that wasn't written by someone who was just eager to apply their hard-learned OOP concepts, and you'll see that points, like every other simple thing in the world that are just plain-old data, have their member variables public.
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