Four ways to define functions in Kotlin

FunctionTest.kt

package i_introduction._4_Lambdas

import org.junit.Assert
import org.junit.Test

class FunctionTest {
    // C-style declared function with block body
    fun inc_block(i: Int): Int {
        return i + 1
    }

    // declared function with expression body
    fun inc(i: Int): Int = i + 1

    // inline function with expression body
    val inc_var = { i: Int -> i + 1 }

    // inline function with block body
    // unlike Dart, this infers the return type
    // (I checked this via hitting Ctrl+Q in IntelliJ IDEA.)
    val inc_var_block = { i: Int ->
        val result = i + 1
        result
        // return keyword is actually forbidden in lambda-expressions
    }

    // but it's also easy to specify the type of a function-value variable:
    val inc_var_explict: (Int) -> Int = inc_var_block

    @Test
    fun allTests() {
        Assert.assertEquals(2, inc(1))
        Assert.assertEquals(2, inc_block(1))

        Assert.assertEquals(2, inc_var(1))
        Assert.assertEquals(2, inc_var_block(1))
        Assert.assertEquals(2, inc_var_explict(1))
    }
}