Declare for loop as an array of variables [duplicate]

Question

My goal is to store the variable in the for loop as an array rather than as a single 'ultrasoundValue'. Can some one help me structure the code?

I have this code:

int ultraSoundSignalPins[] = {5,7}; 
int tx = 4;
char *pingString[] = {"Ping1 ","Ping2 "}; // just something to print to             indicate direction

void setup()
{
 Serial.begin(9600);
}

void loop()
{

 unsigned long ultrasoundValue;
 for(int i=0; i < 2; i++)
 {
   ultrasoundValue = ping(i);
   Serial.print(pingString[i]);
   Serial.print(ultrasoundValue);
   Serial.print("cm, ");    
   delay(500);

 }
} 

//Ping function
unsigned long ping(int i)
{
 unsigned long echo;

 pinMode(ultraSoundSignalPins[i], OUTPUT); // Switch signalpin to output
 pinMode(tx, OUTPUT);          
 digitalWrite(ultraSoundSignalPins[i], LOW); // Send low pulse
 digitalWrite(tx, LOW); 
 delayMicroseconds(2); // Wait for 2 microseconds
 digitalWrite(ultraSoundSignalPins[i], HIGH); // Send high pulse
 digitalWrite(tx, HIGH);
 delayMicroseconds(5); // Wait for 5 microseconds
 digitalWrite(ultraSoundSignalPins[i], LOW); // Holdoff
 pinMode(ultraSoundSignalPins[i], INPUT); // Switch signalpin to input
 digitalWrite(ultraSoundSignalPins[i], HIGH); // Turn on 0pullup resistor
 echo = pulseIn(ultraSoundSignalPins[i], HIGH); //Listen for echo
 return (echo / 29.1); //convert to CM then to inches
}

Answer 1

Make ultrasoundValue an array and use i as the index to it? Just like you have with all your other arrays?

You obviously know how to use arrays, since you have already been using them throughout your code.

Answer 2

You don't even have to add any lines, just modify a couple!

unsigned long ultrasoundValue [2]; //creates an array of unsigned longs of size 2

...and inside your for loop:

ultrasoundValue[i] = ping(i);

It appears you are acquiring 2 separate ultrasound values. If you'd like to store multiple sets of these 2 values, you could use a two-dimensional array:

unsigned long ultrasoundValue [10][2]; //an array of 10 pairs of long unsigned values

...and you could modify your for loop to have a pair of nested for loops:

 for (int i = 0; i < 10; i++)
 {
   for (int j = 0; j < 2; j++)
   {
      ultrasoundValue[i][j] = ping(j);
      //do whatever else
   }
 }