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[手动选题][tech]: 20230109.0 ⭐️⭐️ Learn the Ada programming language by writing a simple game.md
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[#]: subject: "Learn the Ada programming language by writing a simple game"
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[#]: via: "https://opensource.com/article/23/1/learn-ada-simple-game"
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[#]: author: "Moshe Zadka https://opensource.com/users/moshez"
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[#]: collector: "lkxed"
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[#]: translator: " "
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[#]: reviewer: " "
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[#]: publisher: " "
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[#]: url: " "
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Learn the Ada programming language by writing a simple game
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======
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When you want to [learn a new programming language][1], it's good to focus on the things programming languages have in common:
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- Variables
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- Expressions
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- Statements
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These concepts are the basis of most programming languages. Once you understand them, you can start figuring out the rest. Because programming languages usually share similarities, once you know one language, you can learn the basics of another by understanding its differences.
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A good way to learn new languages is practicing with a standard program. This allows you to focus on the language, not the program's logic. I'm doing that in this article series using a "guess the number" program, in which the computer picks a number between one and 100 and asks you to guess it. The program loops until you guess the number correctly.
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This program exercises several concepts in programming languages:
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- Variables
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- Input
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- Output
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- Conditional evaluation
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- Loops
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It's a great practical experiment to learn a new programming language.
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### Install Ada
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The [Ada programming language][2] is a unique and highly structured language with a dedicated developer base. The toolchain for Ada is the GNU Ada Development Environment, better known as GNAT.
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You can install GNAT on Linux using your distribution's package manager. On Fedora, CentOS, or similar:
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```
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$ sudo dnf install gcc-gnat
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```
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On Debian, Linux Mint, and derivatives:
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```
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$ sudo apt install gnat
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```
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On macOS and Windows, you can download an installer from the [Adacore website][3] (choose your platform from the drop-down menu).
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### Guess the number in Ada
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Create a file called `game.adb`.
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The two built-in Ada libraries this program uses are `Text_IO` and `Numerics.Discrete_Random`:
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```
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with Ada.Text_IO;
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use Ada.Text_IO;
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with Ada.Numerics.Discrete_Random;
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```
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#### Procedure head
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The name of the procedure must match the name of the file. The first part is defining the variables.
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Note that the `discrete_random` is specialized to a specific range. In this case, the range of numbers allowed:
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```
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procedure Game is
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type randRange is range 1..100;
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package Rand_Int is new ada.numerics.discrete_random(randRange);
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use Rand_Int;
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gen : Generator;
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num : randRange;
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incorrect: Boolean := True;
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guess: randRange;
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```
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#### Procedure logic
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The logic starts by `reset(gen)`. This initializes the random number generator, ensuring the number, initialized with `random(gen)`, will be different each time you run the program.
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The next step is to run the loop:
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- Output the instructions for a guess
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- Read the line
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- Convert it to `randRange`
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- Check it against the number
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If the number matches, incorrect is set to **False**, causing the next iteration of the loop to exit.
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Finally, the program prints a confirmation of the guess correctness before exiting:
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```
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begin
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reset(gen);
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num := random(gen);
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while incorrect loop
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Put_Line ("Guess a number between 1 and 100");
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declare
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guess_str : String := Get_Line (Current_Input);
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begin
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guess := randRange'Value (guess_str);
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end;
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if guess < num then
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Put_line("Too low");
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elsif guess > num then
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Put_line("Too high");
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else
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incorrect := False;
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end if;
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end loop;
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Put_line("That's right");
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end Game;
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```
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### Build the program
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The easiest way to compile an Ada program is to use `gnatmake`:
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```
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$ gnatmake game.adb
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aarch64-linux-gnu-gcc-10 -c game.adb
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aarch64-linux-gnu-gnatbind-10 -x game.ali
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aarch64-linux-gnu-gnatlink-10 game.ali
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```
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This generates a binary called `game`.
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### Run the program
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Each run of the program will be a little different. This is one example:
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```
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$ ./game
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Guess a number between 1 and 100
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50
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Too low
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Guess a number between 1 and 100
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75
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Too low
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Guess a number between 1 and 100
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82
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Too low
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Guess a number between 1 and 100
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90
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Too high
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Guess a number between 1 and 100
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87
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Too low
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Guess a number between 1 and 100
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88
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That's right
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```
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### Learn Ada
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This "guess the number" game is a great introductory program for learning a new programming language because it exercises several common programming concepts in a pretty straightforward way. By implementing this simple game in different programming languages, you can demonstrate some core concepts of the languages and compare their details.
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Do you have a favorite programming language? How would you write the "guess the number" game in it? Follow this article series to see examples of other programming languages that might interest you!
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/23/1/learn-ada-simple-game
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作者：[Moshe Zadka][a]
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选题：[lkxed][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/moshez
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[b]: https://github.com/lkxed
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[1]: https://opensource.com/article/20/10/learn-any-programming-language
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[2]: https://opensource.com/article/21/10/learn-ada-2021
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[3]: https://www.adacore.com/download/more
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