Currying at Five Levels

1. Child:

Imagine you’re making a sandwich, but you don’t have all the ingredients at the same time. You get the bread now, the peanut butter a little later, and the jelly last. Even though you add each part at a different time, you still end up with a peanut butter and jelly sandwich. That’s what currying in programming is like! It’s a way to build something, like a sandwich, one part at a time.

2. Teenager:

Let’s say you’re playing a video game where you have to collect different parts to build a machine. You can collect these parts in any order and at any time, but you need all of them to build the machine. Currying in programming is similar. It allows you to create a function that can be called multiple times with one or more arguments, until all the necessary arguments have been provided. Only then is the final result calculated.

3. College student (not a CS major):

In mathematics, you might have seen functions like f(x, y, z). Now, what if you have the value for x, but not yet for y and z? This is where currying comes in handy. Currying is a technique in programming where a function with multiple arguments is broken down into a sequence of functions, each with a single argument. It allows you to pass one argument at a time, and each function returns another function that takes the next argument, until all arguments are supplied and the final value is returned.

4. Computer Science Undergraduate:

Currying is a technique in functional programming where a function with multiple arguments is transformed into a series of functions, each taking a single argument. It’s a way to partially apply functions. In other words, you can create a new function by providing fewer arguments than the original function needs. This new function, when called, will hold the provided arguments “fixed” and will take the remaining arguments to complete the operation.

5. Grad student/Colleague:

Currying, named after Haskell Curry, is a significant concept in functional programming and lambda calculus. It is the process of decomposing a function of multiple arguments into a chain of functions each taking a single argument. It’s particularly powerful when combined with higher-order functions, as it allows for function composition and more efficient code reuse. Currying supports partial function application where you can fix a number of arguments and produce a new function that accepts the remaining ones. Languages like Haskell support currying natively, while in languages like JavaScript, you would need to implement currying explicitly.

Richard Feynman Explanation

Alright, so let’s imagine you’re making a sandwich. Now, when you’re making a sandwich, you don’t just slam everything together at once, right? You go one step at a time. First, you take out a slice of bread, then you add some lettuce, next comes the cheese, then the tomato, and finally you top it off with another slice of bread. Each step is dependent on the step before it, and you can’t just skip ahead without messing up the sandwich.

Currying in programming is sort of like that process. When you have a function that takes multiple arguments, currying lets you break down that function into a series of functions, each taking one argument and returning another function that takes the next argument, just like adding one ingredient at a time to your sandwich.

For instance, if you have a function that adds three numbers together, instead of calling it like add(1, 2, 3), with currying you can do add(1)(2)(3). This gives you a lot more flexibility with how you apply your arguments. You could even decide to apply some arguments now and some later, like preparing the bread and lettuce for your sandwich in the morning and adding the cheese and tomato later at lunch.

Just like preparing your sandwich in stages can make your morning routine more flexible and efficient, currying your functions can make your code more flexible and reusable. It’s just another tool in your coding toolbox, and when used in the right way, it can be really powerful.

Imagine you’re cooking a meal. Cooking often requires doing things in a certain order. You can’t bake the cake before you mix the ingredients, and you can’t mix the ingredients before you’ve got them all out on the counter, right?

Now, when you’re preparing your meal, you might find that some steps can be done ahead of time. For example, you could pre-mix the dry ingredients for your cake, put them in a container, and then add the wet ingredients later when you’re ready to bake.

Currying is kind of like that. It’s a way to prepare a function in stages.

Suppose you have a function that adds three numbers together. A regular function would take all three numbers at once. But a curried function would take one number, then return a new function that takes the second number, and then that function would return another new function that takes the third number.

So, just like how you might pre-mix the dry ingredients for your cake to make the baking step easier later, currying allows you to prepare part of a function ahead of time. This can make your code easier to understand and reuse, much like how preparing part of your meal ahead of time can make the cooking process more manageable.

Q&A

  • Why do we need these different scopes in JavaScript?
  • What problems do they solve?

Currying is a powerful functional programming technique in JavaScript that can help make your code more clean, flexible and efficient. It can be used to simplify your code and improve its reusability, readability, and modularity.

Here are some reasons why we need currying in JavaScript:

  1. Function Reusability: One of the key benefits of currying is that it allows you to create new functions by fixing a subset of arguments. This can lead to more reusable and maintainable code. For instance, you can create a function that adds two numbers, and then use currying to create a new function that increments a number by one.

  2. Delayed Execution: Currying allows you to split your functions into smaller functions that each take just one argument. This can be useful when you don’t have all the arguments needed to get your final value. Each time you pass an argument, you get a new function back that remembers which arguments have been passed so far and only needs the remaining ones.

  3. Increased Readability: When working with higher-order functions, currying can help to reduce the complexity and improve the readability of your code. It allows you to write functions in a way that makes them easier to read and understand.

  4. Functional Techniques: Currying is integral to some functional programming techniques. For instance, it facilitates function composition, where the output of one function serves as the input to another. It also enables point-free programming, a style in which you define functions without mentioning their arguments.

  5. Event Handling and Asynchronous Code: Currying can be used to handle events or asynchronous operations. It allows you to bind data to a function without executing it immediately. The function can then be executed when an event is fired or an asynchronous operation is completed.

In sum, currying provides a way to improve your JavaScript code by making it more modular, readable, and reusable. It helps manage complexity in large codebases and can lead to more robust and maintainable applications.

Currying in React

Currying can be used in JavaScript applications, including React applications, but it’s not necessarily a core part of React or commonly seen in every React application.

React focuses on the component model for building user interfaces, and whether or not you use currying in your React application depends largely on the needs of your specific application and your personal coding style.

That said, currying can be very helpful in specific contexts. For example, you might see currying in event handlers in React. Here’s an example:

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class MyComponent extends React.Component {
  handleClick = (id) => () => {
    // this will create a new function that, when called, will call
    // this.props.onClick with the provided id
    this.props.onClick(id);
  }

  render() {
    return (
      <div>
        {this.props.items.map(item => (
          <div onClick={this.handleClick(item.id)} key={item.id}>
            {item.text}
          </div>
        ))}
      </div>
    );
  }
}

In this code, handleClick is a curried function. When you call handleClick(id), it returns a new function. When that new function is called, it will call this.props.onClick(id). This allows you to create new functions on-the-fly in your render method that have access to specific data (like an item’s id), without needing to manually manage binding this in your constructor.

Still, this is just an example, and there are many different ways to handle events in React. Whether you use currying will depend on your needs, the specific problems you’re trying to solve, and your personal preferences.

Currying vs Template Pattern

While both currying and the Template Method Pattern are used to handle function and method behaviors, they address different concerns and are used in different contexts, so they’re not really similar.

  1. Currying is a functional programming concept where a function with multiple arguments is transformed into a series of functions, each with a single argument. It’s used to generate a flexible and reusable function that can be customized with specific arguments.

    For example, in JavaScript, a simple non-curried function could be:

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    function add(x, y) {
  return x + y;
}

    This could be curried as:

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    function add(x) {
  return function(y) {
    return x + y;
  }
}

    Here, add is a curried function that takes x and returns another function that takes y.

  2. The Template Method Pattern is a behavioral design pattern that defines the skeleton of an algorithm in a superclass but lets subclasses override specific steps of the algorithm without changing its structure. It’s used in object-oriented programming to control the overall flow of the algorithm, but leave the specific steps to be defined or implemented by the subclass.

    For example, in Java, an abstract class that uses the template method pattern could be:

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    public abstract class AbstractClass {
  public void templateMethod() {
    operation1();
    operation2();
  }

  public abstract void operation1();

  public abstract void operation2();
}

public class ConcreteClass extends AbstractClass {
  public void operation1() {
    // implementation...
  }

  public void operation2() {
    // implementation...
  }
}

    Here, templateMethod is a template method that defines the order of operations, but the specific implementations of operation1 and operation2 are left to the ConcreteClass.

So, while both currying and the Template Method Pattern can make your code more flexible and reusable, they’re used for different purposes: currying helps you customize functions in functional programming, while the Template Method Pattern helps you control algorithm flow in object-oriented programming.