C++ Can't Print Values from Array of Strings - c++

Question

I am having trouble with an assignment for my freshman Computer Science class.
I am trying to have PrintAllConcepts print each item of an array, once per line.
For some reason all I get is the last line printed from LIST.txt and a bunch of extra empty lines that usually end up nearly crashing the program. There appears to be no syntactical errors, so I'm afraid I am not reading the concepts into the array correctly. This is where I would like assistance.
Below is my code.
I also apologize if this seems like a noob question, as I am a beginner in C++.
Edit: Also, explaining why the Number parameter is so funky, my assignment seems to be requiring me to do it that way. That is also why PrintAllConcepts and ReadConcepts returns void.
#include <string>
#include <sstream>
#include <iostream>
#include <fstream>
#include <iomanip>
void ReadConcepts(std::string Concepts[100], int &Number) {
std::ifstream fin;
fin.open("LIST.txt");
if (!fin.is_open()) {
std::cerr << "error: file open failed.\n";
}
std::string theConcepts[100];
std::string line;
int i;
for (i = 0; i <= 99; i++) {
while (std::getline(fin, line)) {
theConcepts[i] = line;
Number++;
}
}
}
void PrintAllConcepts(std::string Concepts[100], int Number) {
int i;
std::string line;
for (i = 0; i < Number - 1; i++) {
line = Concepts[i];
std::cout << line << std::endl;
}
std::cout << i;
}
int main() {
// Initiate variables
std::string Concepts[100];
int Number = 100;
// Read concepts
ReadConcepts(Concepts, Number);
// Open file for void function PrintAllConcepts
std::ifstream fin;
fin.open("LIST.txt");
if (!fin.is_open()) {
std::cerr << "error: file open failed.\n";
}
int i;
std::string line;
for (i = 0; i < 99; i++) {
while (std::getline(fin, line)) {
Concepts[i] = line;
}
}
PrintAllConcepts(Concepts, Number);
}

Answer 1

As you commented, the errors are in the ReadConcepts function.
To begin with you should not increment Number in the loop, as it's already the number of elements in the array. Because you increment Number you will pass the value 200 to PrintAllConcepts which will make it go out of bounds of the array.
Secondly you put all strings into the local array theConcepts instead of the array Concepts passed to the function. This means none of the strings in Concepts will be set, giving you the "empty" output. Remove the theConcepts array and use Concepts instead.
Thirdly you should have either the for loop, or the while loop, but not both. Since you have both the first iteration of the for loop will read all lines from the file, putting all of it into theConcepts[0], and leave the rest of the array with empty strings. I recommend a combination of both loops, as in:
for (int i = 0; i < Number && std::getline(fin, line); ++i)
{
Concepts[i] = line;
}
There are also some other "problem" that aren't serious and won't cause any errors. One of them is passing the Number argument by reference. Since Number should not be modified you should pass it by value.

Answer 2

As a perfunctory node to your question, you may want to insert a condition for reading the file in its entirety, i.e., while (fin.good()), etc.
That said, the above hints and tips are second to none. Debugging programs can teach you a lot, and are as good a learning tool as writing the code yourself. I should know; I'm new at this too. Good luck.
p.s.: Don't forget the good practice of closing your file once finished with it.