Function Composition Strategies: 8 Chess-Like Moves to Enhance Your Kotlin Skills with Function Composition

Photo by Randy Fath on Unsplash

“Function composition is a powerful concept in programming where you combine multiple functions to create a new function.”

Have you ever thought about programming as a bit like playing chess, where every choice you make can lead to either a win or a loss? Well, in the world of coding, function composition is the special technique that lets you blend simple actions together, kind of like how chess pieces come together in a master plan.

Now, picture yourself as a clever chess player in the world of coding with Kotlin. Kotlin offers you a bunch of nifty tools that are a bit like chess tactics — you can mix and match them to create your own coding strategies. In this article, we’re going to explore eight ways to combine functions in Kotlin. It’s a bit like learning different chess strategies, but for coding. These techniques give you various options, depending on how you like to approach your code. So, let’s dive right in and discover how you can juggle functions in Kotlin to make your code even smarter.

Technique 1: Sequential Composition

What is it?
This technique calls each function one after the other in a sequence. It’s like following steps in a recipe.

Pros:

• Simple and easy to understand.
• Clear step-by-step execution.

Cons:

• May become verbose with many functions.
• Limited flexibility for complex compositions.

Example:

fun sayHelloToEveryone() {
    hello1()
    hello2()
    hello3()
    hello4()
    hello5()
}

Technique 2: Nested Function Invocation

What is it?
Nested function invocation calls one function within another, creating a chain of function calls. It’s like opening a series of nested boxes.

Pros:

• Allows flexibility in composing functions.
• Useful for creating complex workflows.

Cons:

• Can become hard to read with deep nesting.
• Doesn’t promote reusability.

Example:

fun sayHelloToEveryone2() {
    hello1(
        hello2(
            hello3(
                hello4(
                    hello5()
                )
            )
        )
    )
}

Technique 3: Declarative Nested Function Invocation

What is it?
This approach combines nested function invocation with clear, declarative style. It’s like telling a story with a series of function calls.

Pros:

• Enhances readability and maintainability.
• Supports a more expressive coding style.

Cons:

• Still subject to deep nesting issues.
• May require additional code for reusability.

Example:

fun sayHelloToEveryone3(): Int {
    val hello1 = hello1()
    val hello2 = hello2(hello1)
    val hello3 = hello3(hello2)
    val hello4 = hello4(hello3)
    return hello5(hello4)
}

Technique 4: Fluent Interface Style or Function Chaining

What is it?
Fluent interface style allows functions to be chained together using a dot notation. It’s like a conveyor belt where each station performs a specific task.

Pros:

• Promotes a clean and fluent coding style.
• Reduces nesting and enhances readability.

Cons:

• Requires additional code to support chaining.
• May not work well for complex compositions.

Example:

fun sayHelloToEveryone4() {
    hello1()
        .hello2()
        .hello3()
        .hello4()
        .hello5()
}

Technique 5: Domain-Specific Language (DSL)

What is it?
A DSL is a specialized language for a particular domain or problem. It allows you to create functions that read like a domain-specific language, enhancing expressiveness.

Pros:

• Enhances readability by creating a custom, domain-specific syntax.
• Simplifies complex tasks in specific domains.

Cons:

• Requires designing and implementing a DSL.
• May not be suitable for all projects.

Example:

// DSL creation
fun sayHello(init: HelloDSL.() -> Unit): HelloDSL {
    val helloDSL = HelloDSL()
    helloDSL.init()
    return helloDSL
}


// DSL usage
fun main() {
    sayHello {
        hello1()
        hello2()
        hello3()
        hello4()
        hello5()
    }
}

Technique 6: Nested Higher-Order Function Invocation

What is it?
Similar to nested function invocation, but with higher-order functions. It’s like passing functions as arguments to other functions within a chain.

Pros:

• Enables complex behavior composition.
• Supports asynchronous or parallel execution.

Cons:

• Requires a solid understanding of higher-order functions.
• Can lead to complex code when overused.

Example:

// Example creation of high order function
fun hello1(runFunction: () -> Unit) {
    runFunction()
}

// Usage
fun sayHelloToEveryone5() {
    hello1 {
        hello2 {
            hello3 {
                hello4 {
                    hello5()
                }
            }
        }
    }
}

Technique 7: Function Composition Operators

What is it?
Function composition operators like compose and andThen combine functions to create new functions. It’s like building more advanced machinery from basic tools.

Pros:

• Promotes code reusability and readability.
• Offers a clear and concise way to express function composition.

Cons:

• Requires familiarity with the operator syntax.
• Limited to linear composition; may not handle complex branching well.

Example:

val composedHello = hello1 andThen hello2 andThen hello3
composedHello()

Technique 8: Using a List of Functions

What is it?
Using a list of functions involves storing functions in a list and then iterating through the list to execute them. It’s like having a playlist of functions.

Pros:

• Allows dynamic selection and execution of functions.
• Simplifies the management of multiple functions.

Cons:

• Limited to predefined functions in the list.
• May introduce overhead when maintaining a large list.

Example:

val helloFunctions = listOf(hello1, hello2, hello3, hello4, hello5)

fun sayHelloToEveryone6() {
    for (sayHello in helloFunctions) {
        sayHello()
    }
}

Ending Remarks

In conclusion, achieving function composition in Kotlin is a bit like mastering different chess strategies. Depending on the complexity of your code and the expressiveness you need, you can choose from these eight techniques. Each has its own advantages and disadvantages, so it’s important to pick the one that suits your coding style and project requirements.

Just as a skilled chess player can adapt their strategy to any game, a proficient Kotlin coder can use these techniques to craft elegant and efficient code. So go ahead, experiment with these methods, and elevate your coding game.

Photo by Randy Fath on Unsplash

This article was previously published on proandroiddev.com