Ignoring negative numbers and moving on

This is a discussion on Ignoring negative numbers and moving on within the C++ Programming forums, part of the General Programming Boards category; I am trying to read from a file of integers, when the program encouters -1 then it is to skip ...

  1. #1
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    Question Ignoring negative numbers and moving on

    I am trying to read from a file of integers, when the program encouters -1 then it is to skip over it and continue reading more integers that follow it. I was thinking about using fin.ignore, but anything I try with it doesn't seem to be working. Does anybody have any suggestions or resources I could use?

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    Continue might be a good word to use. (I'm assuming that the only thing you're supposed to skip is the -1, which you've already read in, so there's nothing to ignore.)

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    clarification

    I'm not sure you understood what I was saying, let me give an example.

    You have some input like this:

    1 2 3 4 5 6 -1 7 8 9 10

    When you reach (-1) you should print out the numbers up untill then, then move on to the next set of numbers.

    The problem I'm having is that I can read in and print the first set of number, but when I try to move on the next output includes the (-1) and doesn't move on.

    What I'm working on specifically is loading these numbers into a tree. So the first set of numbers goes into tree1, you hit the -1, skip it, and put the next set of numbers in tree2. The specific problem I'm having is that it is not skipping -1, it's loading it into tree2 and then stopping there.

    Here is the code I am working on that I am facing this problem with:

    Code:
    while (fin>>num)
    	{
    
    		if(num>=1) //If the number is greater than or equal to one (meaning not -1)
    		{
    			Tree[1].insert(num); //Insert that number into tree 1
    			compareInsert ++;
    		}
    		else
    		{
    			/*if (fin.peek() == '-' && fin.peek() == 1)
    			{
    				fin.ignore(1,-1);
    			}*/
    
    			for (int i=2; i < 10; i++) //Starting at tree 2
    			{
    				Tree[i].insert(num); //Insert next set of numbers
    			}
    		}
    
    	}
    As you may see, I tried using the peek and ignore function but the way I had it was not working, I also tried it several different ways, but had no luck.

    Any suggestions on how to fix this?

  4. #4
    and the Hat of Guessing tabstop's Avatar
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    So, is 7 8 9 10 considered "the next set of numbers"? Or do we mean, skip the rest of the line?

  5. #5
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    have you tried something like
    Code:
    {
    		while ( fin >> num )
    			if ( num < 0 )
    			{
    				print_numbers();//whatever
    				fin >> num;
    				//start over again
    			}
    	}
    edit: it is incomplete on purpose. so please dont call me stupid.

  6. #6
    and the Hat of Guessing tabstop's Avatar
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    On the assumption that 7 8 9 10 is the next set of numbers, all you have to do is
    Code:
    current_tree_number = 0;  //I don't know why you start at 1 and leave the first tree blank
    while (fin >> num) {
        if (num == -1) {
            current_tree_number++;
            //maybe print it out if you want
            //note the complete absence of ignoring things, since the -1 is already gone
        }
        else {
            Tree[current_tree_number].insert(num);
            compareInsert++; //whatever this does
        }
    }

  7. #7
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    Thanks

    Thanks tabstop, that did the trick. I was trying to do things the hard way and it turned out so simple!

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