Скачать или смотреть Mastering C+ + 17 Fold Syntax: Testing Vector Composition Made Simple

Learn how to leverage `C+ + 17` fold syntax to implement powerful vector composition functions. Explore `any`, `all`, and `only` functions with practical examples.
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Mastering C+ + 17 Fold Syntax: Testing Vector Composition Made Simple

C+ + 17 introduced several powerful features that simplify coding tasks, one of which is fold expressions. Particularly useful when dealing with sequences, fold expressions can help create clean and efficient functions. This guide will delve into how to use C+ + 17 fold syntax to test vector composition effectively. We'll define common functions such as any, all, and will also explore the creation of a function called only.

Understanding the Problem

When working with collections in C+ + , you often need to check for the presence of certain values within vectors or arrays. The standard approaches involve writing loops or using standard library functions, which can become cumbersome. With C+ + 17's fold expressions, we can streamline this process.

Here are a few key functions we'll implement:

any: Checks if any of the values are present in the vector.

all: Checks if all the specified values are present in the vector.

only: Checks if the set of unique values in the vector matches the provided input values.

Implementing any and all Functions

Let’s dissect how to create the any and all functions using fold expressions.

The contains Function

Before implementing any and all, we need a helper function called contains, which verifies the presence of a single value in a collection. Here’s how it's done:

[[See Video to Reveal this Text or Code Snippet]]

The any Function

The any function checks if at least one of the specified values exists in the vector.

[[See Video to Reveal this Text or Code Snippet]]

The all Function

Similarly, the all function ensures that all specified values exist in the vector:

[[See Video to Reveal this Text or Code Snippet]]

Example Usage

Here’s how you can test the any and all functions with an array:

[[See Video to Reveal this Text or Code Snippet]]

Creating the only Function

Now that we’ve established any and all, let’s develop the only function. This function will return true if the unique values of the vector match the given input values.

Initial Implementation

Here’s a straightforward implementation of the only function:

[[See Video to Reveal this Text or Code Snippet]]

Enhanced Implementation Using Count_if

We can enhance the only function using the standard algorithm std::count_if, which will make our code cleaner:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

C+ + 17 fold expressions significantly simplify how we handle vector composition tests. By implementing the any, all, and only functions, you can efficiently check for value presence in vectors without using complex structures. This not only enhances code readability but also maintains performance.

Feel free to test out these functions and see how they streamline your C+ + coding experience! Happy coding!