What is partial?
Partial, short for partial application, is a technique in programming where you take a function that needs several arguments and fix some of those arguments in advance, creating a new function that requires fewer arguments.
Let's break it down
- Imagine a function add(a, b) that adds two numbers.
- With partial application you can “pre‑load” the first argument, say a = 5, and get a new function add5(b).
- Now you only need to supply the second argument when you call add5, and it will return 5 + b.
Why does it matter?
Partial application lets you build more specific, reusable functions from general ones, reduces repetition, and makes code easier to read and compose, especially in functional programming styles.
Where is it used?
- Functional languages like Haskell, Elm, and F# have built‑in support.
- In JavaScript you can use libraries such as lodash’s _.partial or the native bind method.
- C# and Java can achieve it with lambda expressions or helper methods.
- It’s common in UI frameworks (e.g., React) to pre‑configure event handlers.
Good things about it
- Encourages modular, composable code.
- Cuts down on boilerplate by reusing existing functions.
- Improves readability by giving functions meaningful names (e.g., add5).
- Works well with higher‑order functions and pipelines.
Not-so-good things
- Can add a layer of indirection that makes debugging harder if overused.
- May introduce slight performance overhead from creating extra wrapper functions.
- Not all languages have native syntax, so you might need extra libraries or verbose code.