Tartarus

unholy-curry

Enables currying for function/lambda/constructor

Why Currying
Gradle Setup
Examples
Advanced Examples

Why Currying

@Curry
fun testHotness(person: String, chili: String) {}

val chilis = listOf("Cayenne","Habanero", "Carolina Reaper")

// normally
chilis.map{chili -> testHotness("Peter", chili)}

// with currying, you can preload the function
val testerPeter = testHotness("Peter")
chilis.map(testerPeter)

Gradle Setup

apply plugin: 'kotlin-kapt'

repositories {
    maven { url 'https://jitpack.io' }
}

dependencies {
    kapt 'in.abaddon.tartarus:unholy-curry:0.0.4'
    compileOnly 'in.abaddon.tartarus:unholy-curry:0.0.4'
}

Examples

annotate function/lambda/constructor with @Curry
import subpackage curry
have fun ;)

package com.example.foo

import com.example.foo.curry.*

class Spice
@Curry constructor(val name: String, val color: Int, hotness: Int) {

    @Curry
    val enhance = {factor: Double, quantity: Int, degree: Int ->  ... }

    @Curry
    fun mitigate(drink: String, quantity: Int, degree: Int): Int { ... }
}

object MainObj {
    fun doSomething() {
        val s1 = Spice("GhostPepper",0xF00,1000000)
        s1.enhance(2.5, 50, 90)
        s1.mitigate("Milk",100,90)
        
        // with currying
        val s2 = createSpice("GhostPepper")(0xF00)(1000000)
        s2.enhance(2.5)(50)(90)
        s2.mitigate("Milk")(100)(90)
    }
}

Advanced Examples

Recap:

Method signature consists of method name and ordered parameter list

Only types are significant for the parameter list and the name of parameter is ignored

The return type is not included

Rename

It could happen that generated curried function clashes with the existing method signature. In such a case, you can simply override the name.

class Pan {   
    fun cook(ingredients: String) { ... }

    // Requires custom name because the curried function will clash with method signature above.
    @Curry(name = cookSmoothly)
    fun cook(ingredients: String, heat: Int, duration: Double){ ... }
}

pan.cook("chicken", 90, 5.0)
pan.cookSmoothly("chicken")(90)(5.0)

Rearrange parameters

We'd like to preload the function cook and apply it to the list of meats. Unfortunately the parameter meat: String, which is needed for the map function, is at the beginning. We can rearrange the order of the parameters for curried function by passing a list of indexes of parameters in the desired order.

class Pan {
    @Curry(order = intArrayOf(1,2,0)) // (heat, duration, meat)
    fun cook(meat: String, heat: Int, duration: Double){ ... }
}

val cookWellDone = pan.cook(/*heat*/ 95)(/*duration*/ 10.0)
listOf("Chicken","Beef","Pork").map(cookWellDone)

bigaru / tartarus