x-- ; // decrement x by one and returns the old value of x

x++; // increment x by one and returns the old value of x ++x; // increment x by one and returns the new value of x

x-- ; // decrement x by one and returns the old value of x @] --x ; // decrement x by one and returns the new value of x @]

x: an integer or long (possibly unsigned)

The original or newly incremented / decremented value of the variable.

y = ++x; // x now contains 3, y contains 3 y = x--; // x contains 2 again, y still contains 3 @]

[@x = 2;

x++; // x now contains 3 x--; // x contains 2 again@]

Description

+=\\

+= -=

[@

x-- ; // equivalent to the expression x = x - 1; @]

++ (increment) / -- (decrement)

Description

The ++ operator is

The -- operator is equivalent to the expression x = x - 1;

Increment or decrement a variable

Syntax

x++ ; // equivalent to the expression x = x + 1; x-- ; // equivalent to the expression x = x - 1;

Parameters

x: any variable type

Returns

Incremented or decremented variable

Examples

x = 2;    // x now contains 2
x++;        // x now contains 3
x--;        // x contains 2 again

Example Code

// check a sensor every 10 times through a loop
void loop(){
i++;
if ((i % 10) == 0){          // read sensor every ten times through loop
   x = analogRead(sensPin);   
   }
/ ...
}

// setup a buffer that averages the last five samples of a sensor

int senVal[5];  // create an array for sensor data
int i, j;       // counter variables
long average;   // variable to store average
...

void loop(){
// input sensor data into oldest memory slot
sensVal[(i++) % 5] = analogRead(sensPin); 
average = 0;
for (j=0; j<5; j++){
average += sensVal[j];   // add up the samples
}
average = average / 5;  // divide by total

Tip

the modulo operator will not work on floats

See also

division

++ (increment)

Increment a variable

Syntax

x++;