Why is my variable jumping in value when I add an "if" condition?

The code below, without the if statement, count’s up from 1 to infinite and shows this in the console as intended.
If I add the if statement, I get what’s shown in the screenshot below. Why does this happen?

#include <Arduino_MKRIoTCarrier.h>
MKRIoTCarrier carrier;
int a;
int r,g,b;


void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
  // Initialize serial and wait for port to open:
  Serial.begin(9600);
  // This delay gives the chance to wait for a Serial Monitor without blocking if none is found
  delay(1500); 
  carrier.begin();
  carrier.display.setRotation(0);
  a =1;


}

void loop() 
{
  // put your main code here, to run repeatedly:
  
  Serial.println(a);
  a =a + 1;

if (a = 10)
    {
      carrier.leds.setPixelColor(0, 255, 0, 0);
      carrier.leds.show();
    }
}

>Solution :

In c++, comparison is ==, so you need to write if (a == 10). When you write, a = 10, that’s an assignment: a will have the value of 10 and the evaluation value is also 10 (to be precise, reference to a which is 10), thus in if() it evaluates to true.