Member Avatar for gretty

Hello

I am reading a text file & I want to make a for loop, loop repeatedly until the end of the file.

Is my code below correct, in terms of syntax? Is this possible to do.

#include <cstdlib>
#include <iostream>
#include <fstream>
#include <string>
using namespace std;


// function prototypes
void printMenu();

int main()
{
	const int MAX = 250000;
	string words[max];
	int nWord;

	ifstream dict;
	dict.open("dict.txt");
	if (dict.fail())
	{
		cout << "No dictionary file" << endl;
		system("pause");
		return 0;
	}
	// read dictionary into array to make multiple searches faster

	while (dict) {
		for (int i=0; i<dict.eof; i++) { // This is the loop I am referring to :)
			getline(dict,words[i],'\n');
			nWord = i;
		}
	}

	cout << nWord << endl << endl;

	if (nWord > MAX) {
		cout << "Error - Dictionary size of out of bounds";
		system("pause");
		return 0;
	}
  • 4 Contributors
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  • Latest Post Latest Post by gretty

Dani AI

Generated

Good instinct to switch to a loop driven by the read itself rather than by eof. In C++ streams, eof() becomes true only after you try to read past the end, so a while(!eof()) loop will often process the last line twice. That explains the issue pointed out with the duplicate, and why ’s approach is on the right track. Also, note that eof is a function, not a data member; writing dict.eof will not compile.

Since your assignment requires an array, the safest pattern is to let std::getline control the loop and also guard against overflowing the array. Keep a running count so you know how many lines you actually stored.

// read up to MAX lines safely; nWord ends as the count of lines read
int nWord = 0;
for (; nWord < MAX && std::getline(dict, words[nWord]); ++nWord) {
    // no body needed; the condition controls EOF and errors
}
std::cout << nWord << '\n';

Tips that will save you time:

  • Drop the outer while(dict) you had; it is redundant once the for condition tests std::getline.
  • If you must support very large dictionaries, consider that an array of 250,000 std::string objects can blow the stack when declared locally. Make it static (static std::string words[MAX];) or move it to file scope to avoid a stack overflow, or use a dynamic container when the assignment allows.
  • Printing nWord gives you the number of lines read; if you later index into words, valid indices are [0, nWord).

Recommended Answers

All 5 Replies

Member Avatar for kvprajapati 
for (int i=0; getline(dict,words[i],'\n'); i++) { 
  ..
}
Member Avatar for poncho4all

you could use

while(!dict.eof())//this will make it keep going untill the end of line
{
dict.getline(words,sizeof(dict));//this will read line by line 
}

hope it helps

Member Avatar for Ancient Dragon

line 14: where is max declared? Note that max is not the same as MAX.

You should use a <vector> instead of string array for two purposes: 1) avoid unnecessary memory allocation, 2) avoid possibility of array overflow (adding too many strings). The <vector> or <list> class will take care of both those problems for you.

Member Avatar for Ancient Dragon

you could use

while(!dict.eof())//this will make it keep going untill the end of line
{
dict.getline(words,sizeof(dict));//this will read line by line 
}

hope it helps

Not really -- that loop will cause the last line to be inserted into the array twice.

>>,sizeof(dict)
You mean sizeof(word), assuming word is a character array instead of std::string.

Member Avatar for gretty

line 14: where is max declared? Note that max is not the same as MAX.

You should use a <vector> instead of string array for two purposes: 1) avoid unnecessary memory allocation, 2) avoid possibility of array overflow (adding too many strings). The <vector> or <list> class will take care of both those problems for you.

I agree, I have just learnt vectors & thats what i would use also. But this is an ssinment & they are making us use an array.

Thx

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