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157 lines
4.2 KiB
Markdown
157 lines
4.2 KiB
Markdown
[#]: collector: (lujun9972)
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[#]: translator: ( )
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (The feature that makes D my favorite programming language)
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[#]: via: (https://opensource.com/article/20/7/d-programming)
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[#]: author: (Lawrence Aberba https://opensource.com/users/aberba)
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The feature that makes D my favorite programming language
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======
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UFCS gives you the power to compose reusable code that has a natural
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flow without sacrificing convenience.
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![Coding on a computer][1]
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Back in 2017, I wrote about why the [D programming language is a great choice for development][2]. But there is one outstanding feature in D I didn't expand enough on: the [Universal Function Call Syntax][3] (UFCS). UFCS is a [syntactic sugar][4] in D that enables chaining any regular function on a type (string, number, boolean, etc.) like its member function of that type.
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If you don't already have D installed, [install a D compiler][5] so you can [run the D code][6] in this article yourself.
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Consider this example code:
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```
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// file: ufcs_demo.d
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module ufcs_demo;
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import std.stdio : writeln;
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int[] evenNumbers(int[] numbers)
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{
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import std.array : array;
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import std.algorithm : filter;
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return numbers.filter!(n => n % 2 == 0).array;
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}
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void main()
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{
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writeln(evenNumbers([1, 2, 3, 4]));
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}
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```
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Compile this with your favorite D compiler to see what this simple example application does:
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```
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$ dmd ufcs_demo.d
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$ ./ufcs_demo
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[2, 4]
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```
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But with UFCS as a built-in feature of D, you can also write your code in a natural way:
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```
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...
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writeln([1, 2, 3, 4].evenNumbers());
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...
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```
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or completely remove the now-redundant parenthesis to make it feel like `evenNumbers` is a property:
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```
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...
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writeln([1, 2, 3, 4].evenNumbers); // prints 2, 4
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...
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```
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So the complete code now becomes:
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```
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// file: ufcs_demo.d
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module ufcs_demo;
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import std.stdio : writeln;
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int[] evenNumbers(int[] numbers)
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{
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import std.array : array;
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import std.algorithm : filter;
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return numbers.filter!(n => n % 2 == 0).array;
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}
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void main()
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{
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writeln([1, 2, 3, 4].evenNumbers);
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}
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```
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Compile it with your favorite D compiler and try it out. As expected, it produces the same output:
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```
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$ dmd ufcs_demo.d
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$ ./ufcs_demo
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[2, 4]
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```
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During compilation, the compiler _automatically_ places the array as the first argument to the function. This is a regular pattern that makes using D such a joy, so it very much feels the same as you naturally think about your code. The result is functional-style programming.
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You can probably guess what this prints:
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```
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//file: cool.d
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import std.stdio : writeln;
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import std.uni : asLowerCase, asCapitalized;
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void main()
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{
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string mySentence = "D IS COOL";
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writeln(mySentence.asLowerCase.asCapitalized);
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}
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```
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But just to confirm:
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```
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$ dmd cool.d
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$ ./cool
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D is cool
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```
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Combined with [other D features][7], UFCS gives you the power to compose reusable code that has a natural flow to it without sacrificing convenience.
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### Time to try D
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As I've written before, D is a great language for development. It's easy to install from [the D download page][8], so download the compiler, take a look at the examples, and experience D for yourself.
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/20/7/d-programming
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作者：[Lawrence Aberba][a]
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选题：[lujun9972][b]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://opensource.com/users/aberba
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[b]: https://github.com/lujun9972
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/code_computer_laptop_hack_work.png?itok=aSpcWkcl (Coding on a computer)
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[2]: https://opensource.com/article/17/5/d-open-source-software-development
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[3]: http://ddili.org/ders/d.en/ufcs.html
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[4]: https://en.wikipedia.org/wiki/Syntactic_sugar
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[5]: https://tour.dlang.org/tour/en/welcome/install-d-locally
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[6]: https://tour.dlang.org/tour/en/welcome/run-d-program-locally
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[7]: https://dlang.org/comparison.html
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[8]: https://dlang.org/download.html
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