error <,,.>

**nurulshidanoni** · 04-16-2008

Can somebody tell me whats is the error?

after if
{.....
C:\Documents and Settings\ashida\My Documents\MASTER C++\main\412.cpp(67) : error C2106: '=' : left operand must be l-value

Code:

#include <iostream>   // std::cout
#include <fstream>
#include <iomanip>
#include <string>    // std::string
#include <vector>    // std::vector<>
#include <algorithm> //std::for each()
using namespace std; // import "std" namespace into global namespace

struct exam
{
int examid;
vector <int> total;
};

void SwapMembers (int items[], int index1, int index2)
{
	int temp;
	temp=items[index1];
	items[index1]=items[index2];
	items[index2]=temp;
}

	int main() 
	{
	ifstream stream1("STA83SOLUTION.txt");
		if ( !stream1.is_open())
		{
		cout << "While opening a file an error is encountered" << endl;
		} 
			else 
			{
			cout << "Fail Di buka....." << endl;
			}
	vector <exam> exams;
	exam aExam;
   int tempExamID;
    int tempTotal;
    stream1 >> tempExamID >> tempTotal;
    aExam.examid = tempExamID;
    aExam.total.push_back(tempTotal); // add this exam code to current student's vector of exam codes
    while (stream1 >> tempExamID >> tempTotal)
    {
        if(tempExamID != aExam.examid)
        {
        exams.push_back(aExam); // no more exam codes for this student.  Add aStudent to students vector
        aExam.total.clear();
        aExam.examid = tempExamID;
        }
        aExam.total.push_back(tempTotal); // add this exam code to current student's vector of exam codes
    }
    exams.push_back(aExam); // no more exam codes for this student.  Add aStudent to students vector
    stream1.close(); // We have read the entire file, so time to close it.
{
	ofstream myfile;
	myfile.open("411.txt");
	
	int temp, flag;
	if (myfile.is_open())
	{
		for (size_t i = 0; i < exams.size(); i++) 
		{
			for (size_t j = 0; j<exams.at(i).total.size(); j++) 
			{
				if (exams.at(i).total.size() < exams.at(i).total.size()+1)      // ascending order simply changes to <
				{ 
                    temp = exams.at(i).total.size();             // swap elements
                    exams.at(i).total.size() = exams.at(i).total.size()+1;
                    exams.at(i).total.size()+1 = temp;
                    flag = 1;               // indicates that a swap occurred.
                }

		cout<<"\n"<<i+1<<":"<<" "<< exams.at (i).total.at(j)<<"\t"; // output list of exam codes for this student
	  	cout<<" "<< exams.at (i).total.at(j)<<"\t";
			}
		}
	}
					
cin.get();
return 0;
}
}

**laserlight** · 04-16-2008

You appear to be trying to swap the sizes of the total members of the exam objects when you probably want to swap the total members instead.

Oh, and kindly indent your code more consistently.

**Elysia** · 04-16-2008

It helps to tell at what line the error is occuring.
And the whole indentation is a mess. How did you mess it up so badly whe Visual Studio indents for you? Let it indent for you instead of messing around with it yourself.

**laserlight** · 04-16-2008

It helps to tell at what line the error is occuring.

Line 67, according to the error message... at least that part was included, I get rather frustrated when people cut it off thinking it makes things clearer.

**Elysia** · 04-16-2008

So it says, but I don't want to count the lines and a quick look over the horrible code didn't make anything suspicious point out. I might just have missed it.
Ah, I see it now, thanks to copying it to notepad and using goto line. It's as laserlight says. You're trying to assign a new value to a function, which is impossible.
But in the future, try to mark the line where the error occurs.

**laserlight** · 04-16-2008

So it says, but I don't want to count the lines and a quick look over the horrible code didn't make anything suspicious point out. I might just have missed it.

Visual Studio or any programming text editor worth its bits can give you a line count pretty quickly, methinks. The question then is whether the error message with line number given corresponds to the given source, and in this case it appears to correspond.

**whiteflags** · 04-16-2008

So it says, but I don't want to count the lines

In effect, "I can't be bothered to help."

size() is self-maintained, and you can't swap what is a literal number here. Actually swap the object.

**Elysia** · 04-16-2008

Yeah, but at typing time, I'm not home, so Visual Studio or some other tools are unavailable to me. Although when I thought about it, notepad worked fine.

Originally Posted by citizen

In effect, "I can't be bothered to help."

If you want to put it that way, fine. But it's also my free time, and I'm doing for free, so I'm not obligated to go to extreme lengths, if I feel it is so, to help. A little more from the who who needs help doesn't hurt.

**whiteflags** · 04-16-2008

If you want to put it that way, fine. But it's also my free time, and I'm doing for free, so I'm not obligated to go to extreme lengths, if I feel it is so, to help. A little more from the who who needs help doesn't hurt.

Keeping quiet would have also been a decent alternative, since you really had nothing other than that to say, and the fact that it had been mentioned before.

**nurulshidanoni** · 04-16-2008

so...the error? how to make a correction?

**Elysia** · 04-16-2008

Originally Posted by citizen

Keeping quiet would have also been a decent alternative, since you really had nothing other than that to say, and the fact that it had been mentioned before.

I did point out two other things - namely it's more helpful to point out where the error is and using Visual Studio to indent for you instead of manually.
And I'm not overzealous like some other members who think that it should be made a rule not to reply on posts that aren't helpful in describing the problem.

Originally Posted by nurulshidanoni

so...the error? how to make a correction?

I think you've been told. You shouldn't swap the "size." You should swap the total member instead. The object.

**whiteflags** · 04-16-2008

I love you too.

**matsp** · 04-16-2008

With g++, I get:
t.cpp:67: error: non-lvalue in assignment
t.cpp:68: error: non-lvalue in assignment
Lines 67 and 68 are these:

Code:

                    exams.at(i).total.size() = exams.at(i).total.size()+1;
                    exams.at(i).total.size()+1 = temp;

As was mentioned before, I don't think the size() is what you want to use here.

--
Mats

**~~manav~~** · 04-16-2008

or ... may be size() is supposed to return a reference?

**CornedBee** · 04-16-2008

No, that's the size() of the vector standard class.

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