Kotlin Decrement Operator

In this tutorial, you shall learn about Decrement operator in Kotlin, its syntax, and how to use Decrement operator in programs, with examples.

Kotlin Decrement

Kotlin Decrement Operator takes a variable as operand and decreases the value in variable by one.

-- symbol is used for Decrement Operator.

There are two types of decrement operations based on the position of operand for the operator.

Pre-decrement
Post-decrement

Syntax

The syntax for Decrement Operator is

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//pre-decrement
--operand

//post-decrement
operand--

The operands could be of any numeric datatype.

For Pre-decrement operation, first the value in the variable is decreased by one, and then the value is substituted in the expression or current statement.

For Post-decrement operation, first the current statement is executed, and then the value in the variable is decremented.

Examples

1. Decrement a variable

In the following example, we take an integer value in a, and decrement its value by one using Decrement Operator.

Main.kt

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fun main() {
    var a = 5
    a--
    println("a : $a")
}

Output

a : 4

2. Decrement a decimal value

In the following example, we take a decimal value in a, and decrement its value by one using Decrement Operator.

Main.kt

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fun main() {
    var a = 5.748
    a--
    println("a : $a")
}

Output

a : 4.748

3. Pre-decrement

In the previous examples, we have seen post-decrement operation. But in this example, we will see how a pre-decrement operation works.

In the following example, we take an integer value in a, and pre-decrement its value using Decrement Operator.

Main.kt

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fun main() {
    var a = 5
    var result = --a * 4
    println("a : $result")
}

Output

a : 16

The value in a is decremented by 1, and then that value of a is substituted in the expression.

Now, let us take the same example, but with post-decrement operation.

Main.kt

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fun main() {
    var a = 5
    var result = a-- * 4
    println("a : $result")
}

Output

a : 20

First the expression a * 4 is evaluated, and then the decrement of a happens. If you print the value of a after the third line, then you would observe that the value in a is decremented.

Conclusion

In this Kotlin Tutorial, we learned how to use Decrement Operator to decrease the value in a variable by one.

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