build.gradle

buildscript {
    ext.kotlin_version = '1.2.41'

    repositories {
        mavenCentral()
    }
    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

group 'arrowkt'
version '1.0-SNAPSHOT'

apply plugin: 'kotlin'

repositories {
    mavenCentral()
    jcenter()
}

dependencies {
    compile "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
    compile 'io.arrow-kt:arrow-core:0.7.1'
    compile 'io.arrow-kt:arrow-syntax:0.7.1'
    compile 'io.arrow-kt:arrow-typeclasses:0.7.1'
    compile 'io.arrow-kt:arrow-data:0.7.1'
    compile 'io.arrow-kt:arrow-instances-core:0.7.1'
    compile 'io.arrow-kt:arrow-instances-data:0.7.1'
    kapt    'io.arrow-kt:arrow-annotations-processor:0.7.1'

    compile 'io.arrow-kt:arrow-free:0.7.1' //optional
    compile 'io.arrow-kt:arrow-mtl:0.7.1' //optional
    compile 'io.arrow-kt:arrow-effects:0.7.1' //optional
    compile 'io.arrow-kt:arrow-effects-rx2:0.7.1' //optional
    compile 'io.arrow-kt:arrow-effects-kotlinx-coroutines:0.7.1' //optional
    compile 'io.arrow-kt:arrow-optics:0.7.1' //optional
    compile 'io.arrow-kt:arrow-generic:0.7.1' //optional
}

compileKotlin {
    kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
    kotlinOptions.jvmTarget = "1.8"
}

apply plugin: 'kotlin-kapt' //optional
apply from: rootProject.file('gradle/generated-kotlin-sources.gradle') //optional

apply plugin: 'application'
mainClassName = 'hello.HelloKt'

Hello.kt

package hello

import arrow.core.*
import arrow.typeclasses.*
import arrow.instances.*
import java.util.Collections.list

fun main(args: Array<String>) {
    val a = ForOption extensions {
        binding {
            val a = 123.some().bind()
            val b = 456.some().bind()
            a + b
        }.fix()
    }
    println(a) // => Some(579)
}

transcript.txt

% ./gradlew build
w: /Users/shimada/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-jre7/1.2.31/...snip.../kotlin-stdlib-jre7-1.2.31.jar: kotlin-stdlib-jre7 is deprecated. Please use kotlin-stdlib-jdk7 instead
w: /Users/shimada/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-jre7/1.2.31/...snip.../kotlin-stdlib-jre7-1.2.31.jar: kotlin-stdlib-jre7 is deprecated. Please use kotlin-stdlib-jdk7 instead
w: /Users/shimada/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-jre7/1.2.31/...snip.../kotlin-stdlib-jre7-1.2.31.jar: kotlin-stdlib-jre7 is deprecated. Please use kotlin-stdlib-jdk7 instead
e: /Users/shimada/src/Kotlin/arrowkt/src/main/kotlin/hello/Hello.kt: (9, 13): Classifier 'ForOption' does not have a companion object, and thus must be initialized here
e: /Users/shimada/src/Kotlin/arrowkt/src/main/kotlin/hello/Hello.kt: (10, 9): Unresolved reference: binding
e: /Users/shimada/src/Kotlin/arrowkt/src/main/kotlin/hello/Hello.kt: (11, 32): Unresolved reference: bind
e: /Users/shimada/src/Kotlin/arrowkt/src/main/kotlin/hello/Hello.kt: (12, 32): Unresolved reference: bind

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileKotlin'.
> Compilation error. See log for more details

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 7s
3 actionable tasks: 3 executed

https://twitter.com/pacoworks/status/1004174522365431808

Before 0.7.2 you need to do Option.monad().binding { } instead.