Math with analog input values coming out wrong

Question

Im getting stuck in a while loop because Im having trouble running a calculation on some sensor values. When I read my four sensors values and compare the ratio of the first two to the second two, I keep getting 0.00, no matter what the values are. Here's my code:

while ( ( (frontleft + frontright) / (backleft + backright) <= 0.8 ) || ( (frontleft + frontright) / (backleft + backright) > 1.2) ) {
 if (backleft + backright > frontleft + frontright) {
 myStepper2.step(10);
 }
 if (backleft + backright < frontleft + frontright) {
 myStepper2.step(-10);
 }
 int backleft = analogRead(A0);
 int backright = analogRead(A1);
 int frontleft = analogRead(A2);
 int frontright = analogRead(A3); 
 Serial.print("Backleft Reading: ");
 Serial.println(backleft);
 Serial.print("\n");
 Serial.print("BackRight Reading: ");
 Serial.println(backright);
 Serial.print("\n");
 Serial.print("Frontleft Reading: ");
 Serial.println(frontleft);
 Serial.print("\n");
 Serial.print("Frontright Reading: ");
 Serial.println(frontright);
 Serial.print("\n");
 float ratio = (frontleft + frontright) / (backleft + backright);
 float math = (5 + 6) / (4 + 5);
 Serial.print("Math: ");
 Serial.println(math);
 Serial.print("Ratio: ");
 Serial.println(ratio);
 Serial.print("\n");
 delay(500);
 } 

Im getting values for my sensors (backleft, backright, frontleft, frontright), but 'ratio' always comes out 0.00. Because of that, Im getting trapped in the loop I believe. What's going on here?

Also, just to check, I added 'math' float as that quick calculation, but I'm getting a value of 1.00 in Serial Monitor. Why? It should be 1.222.

Answer 1

Read this: Integer arithmetic and overflow.

float math = (5 + 6) / (4 + 5);
Serial.print("Math: ");
Serial.println(math);

The compiler is treating your expression (the RH side of the "=" sign) as integers. Thus it is working out:

11 / 9 = 1

Then you assign that 1 to a float. Too late to make it a float! It is already truncated.

Try:

float math = float (5 + 6) / float (4 + 5);
Serial.print("Math: ");
Serial.println(math, 4); // 4 decimal places

You get:

Math: 1.2222

---

This also looks wrong:

while ( ( (frontleft + frontright) / (backleft + backright) <= 0.8 ) || ( (frontleft + frontright) / (backleft + backright) > 1.2) ) {
 if (backleft + backright > frontleft + frontright) {
 myStepper2.step(10);
 }
 if (backleft + backright < frontleft + frontright) {
 myStepper2.step(-10);
 }
 int backleft = analogRead(A0);
 int backright = analogRead(A1);
 int frontleft = analogRead(A2);
 int frontright = analogRead(A3); 

How many backleft variables do you have? The one in the while instruction will not be the one you are doing the analogRead on. It doesn't "forward read" variables. I bet you have a different frontleft / backleft etc. set of variables declared earlier. These will not be updated inside the loop.

(To make them get updated drop the word int from inside the loop).