Why doesn't Kotlin support "ternary operator" [closed]

Question

Explain: This question is more about the design intentions of Kotlin. Many expression languages support both Ternary operator and if expression [e.g., Ruby, Groovy.]

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First of all, I know Groovy supports both Ternary operator and Elvis operator: Ternary operator in Groovy. So I don't think it's a syntax problem.

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Then the official documents said:

In Kotlin, if is an expression, i.e. it returns a value. Therefore there is no ternary operator (condition ? then : else), because ordinary if works fine in this role.

And this doesn't convince me. Because Kotlin support Elvis operator which ordinary if works just fine in that role either.

I think ternary operator is sometimes better than ordinary if, though I wonder why doesn't Kotlin just support ternary operator?

Answer 1

In languages which have ternary operator you use it like this

String value = condition ? foo : bar;

In Kotlin you can do the same thing using if and else

var value = if(condition) foo else bar;

Its bit verbose than the ternary operator. But designers of Kotlin have thought it is ok. You can use if-else like this because in Kotlin if is an expression and returns a value

Elvis operator is essentially a compressed version of ternary conditional statement and equivalent to following in Kotlin.

var value = if(foo != null) foo else bar;

But if Elvis operator is used it simplify as follows

var value = foo ?: bar;

This is considerable simplification and Kotlin decided to keep it.

Answer 2

Because if .. else .. works fine. Take a look:

fun main(args: Array<String>) {
    var i = 2

    println("i ${ if(i == 1) "equals 1" else "not equals 1" }")
}

Answer 3

Ternary operator has its problems, for example it is hard to read with big expressions. Here is a line from my C++ project where I used ternary operator:

const long offset = (comm_rank > 0) ? task_size_mod + (comm_rank - 1) * task_size : 0;

I would rather use an if else expression here since it is so much more visible.

Answering you question, I am aware of two reasons why ternary operator was not implemented in Kotlin:

1) Since if else is an expression anyway, it can replace ? :

2) Experience from other languages (C++) shows that ? : provokes hard-to-read code, so it is better to be left out