Thread: rand() error??

hello all, I have this function which is posted below, and the second time the while loop goes through it crashes. On MSVC++ it terminates the dos window, and on unix I get a floating exeption error.

I've pin pointed the problem to be where I get the second random number...near the buttom of the function...any ideas??

axon

Code:

void readInFileAndGetChars(string fileName, char text[], int& sum)
{
	//declaring variables
	int i;

	ifstream inStream;

	inStream.open(fileName.c_str()); //open user chosen file

	if ( inStream.fail() ) { //check if file opened right
		cout << "Input file opening for " << fileName << " failed.  Exiting...\n\n";
		exit(-1);
	}

	for ( i=0; i<MAX_SIZE; i++ ){ //input file into the array
		inStream.get(text[i]);
	}
	
	cout << endl << endl << fileName << " consists of " << MAX_SIZE << " characters.\n\n "
	     << endl;
}

//=============================================
void generateOutput(char text[], int window, int length, int sum)
{
	//declaring arrays
	char *windowArr = new char[window]; //window array
	int allChars[127];

	//declaring variables
	int randomPosition = (rand()/2);//( rand()%MAX_SIZE ); //get random number
	bool notDone = true;
	int i, j, temp;
	int count2 = 0; //couter for how many times through loop
	
	while(notDone)
	{
		int randChar=0;
		int count = 0;	//counter for comparison part
		
		int sum2 = 0;	//sum for all characters that follow window
		char printChar; //randomly chosen charcter that will follow window

		
		for( i=0; i<window; i++){ //match random position characters with window
			if(count2 == 0){	
				windowArr[i] = text[randomPosition + i];
			}else{
				
				windowArr[i] = windowArr[i+1];
				windowArr[window-1] = printChar;
				
			}
		}

		for( i=0; i<127; i++){ //set every element to 0
			allChars[i] = 0;
		}
		
		for( i=0; i<MAX_SIZE; i++){ //COMPARISON
			count = 1;
			if( windowArr[0] == text[i] ){
				for( j=1; j<window; j++ ){
					if( windowArr[j] == text[i+j] ){
						count++;
					}else{ break;}
					if( count == window ){
						allChars[ text[j+i+1]]++; //to get next char and add 1 to it
						break;
					}else{continue;}
				}
			}
		}
		
		for(i=0; i<127; i++){  //get sum of characters which appear at least 1 time
			if(allChars[i] > 0){
				sum2 += allChars[i];
			}
		}
		
		char *lastChar = new char[sum2]; //declare array to hold characters that appear after window
		temp = sum2;
		
		for( i=0; i<127; i++){ //put all characters that appear at least once
			if( allChars[i] > 0 ){ //into an array
				while( temp != -1 ){
					for( j=1; j<=allChars[i]; j++){
						lastChar[i-i+temp-j] = (char)i;
					}
					temp = temp - (1*allChars[i]);
					break;
				}			
			}
		}
		/****The PROBLEM IS IN THE LINE BELOW***/
		randChar = (rand()%sum2); //get random position for next char
		printChar = lastChar[randChar];
		
		cout.flush() << printChar;

		count2++;
		
		if( count2 == length ){
			notDone = false;
		}
	}
}