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Trouble With Input From a File
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I'm getting the same very large number for item and for each element in the array after that for loop is done. Why am i not pulling the 6 numbers from my input file? Thanks.
c Syntax (Toggle Plain Text)
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#2 Oct 27th, 2009
If you only enter one argument then argv[2] is invalid. The program will only have argv[0] and argv[1].
Don't PM me with questions -- you might get a nasty PM in response. If you have a question then post it in one of the forums.
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#3 Oct 27th, 2009
There will always be exactly two arguments that are put in on the command line. The first is the name of the input file (which will also be the output file once renamed) and the second is a # that is the # of floats in the input file to be read.
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#4 Oct 27th, 2009
C++ Syntax (Toggle Plain Text)
Last edited by Dave Sinkula; Oct 27th, 2009 at 9:22 pm.
"One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary." --Ayn Rand
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#6 Oct 27th, 2009
Just sayin'.
#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;
int main(int argc, char *argv[])
{
/* Extract value for # of elements in array */
int i;
sscanf (argv[2], "%d", &i);
// printf("i is %d\n", i);
/* Create Input and Output Streams */
ifstream fin;
ofstream fout;
/* Oprn Input and Output Streams */
fin.open("numlist.dat");
//fout.open("numlist.dat");
/* Tests to ensure files opened */
if(fin.fail())
{
cerr << "Input did not open\n";
exit(2);
}
if(fout.fail())
{
cerr << "Output file did not open\n";
exit(2);
}
/* Construct New Array */
float *floatArray= new float[i];
/* Put numbers from list into array */
float item;
int j=0;
// printf("Put Numbers from list into array\n");
for (j=0; j<i;j++)
{
fin >> item;
printf("item is %f\n", item);
floatArray[j]=item;
printf("floatArray[%d] is %f\n", j, floatArray[j]);
}
}
/* numlist.dat
10 20 30 40 50
*/
/* my output
Debug\cpp.exe file.txt 5
item is 10.000000
floatArray[0] is 10.000000
item is 20.000000
floatArray[1] is 20.000000
item is 30.000000
floatArray[2] is 30.000000
item is 40.000000
floatArray[3] is 40.000000
item is 50.000000
floatArray[4] is 50.000000
*/ Last edited by Dave Sinkula; Oct 27th, 2009 at 9:30 pm.
"One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary." --Ayn Rand
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#7 Oct 27th, 2009
I'm confused why it would be working for you and not for me then. I'm using Visual Studio 2008 for the first time here so that may be it. Where should i be storing my numlist.dat? i have in my source folder along with my msort.cpp file. Is that the problem?
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#8 Oct 27th, 2009
It doesn't work for you because when you open the file for output ofstream truncates it to zero length, erasing all its contents. Comment out ofstream and its open statement then your program will work (after you add the data back into the file again).
Last edited by Ancient Dragon; Oct 27th, 2009 at 10:17 pm.
Don't PM me with questions -- you might get a nasty PM in response. If you have a question then post it in one of the forums.
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