From 6fcf0868ff64dbd23c3bfd9a4c3c8880593edf39 Mon Sep 17 00:00:00 2001 From: DarkSun Date: Thu, 31 Dec 2020 05:01:23 +0800 Subject: [PATCH] =?UTF-8?q?=E9=80=89=E9=A2=98[tech]:=2020201230=20Learn=20?= =?UTF-8?q?Lua=20by=20writing=20a=20"guess=20the=20number"=20game?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit sources/tech/20201230 Learn Lua by writing a -guess the number- game.md --- ...ua by writing a -guess the number- game.md | 131 ++++++++++++++++++ 1 file changed, 131 insertions(+) create mode 100644 sources/tech/20201230 Learn Lua by writing a -guess the number- game.md diff --git a/sources/tech/20201230 Learn Lua by writing a -guess the number- game.md b/sources/tech/20201230 Learn Lua by writing a -guess the number- game.md new file mode 100644 index 0000000000..31d16a8f87 --- /dev/null +++ b/sources/tech/20201230 Learn Lua by writing a -guess the number- game.md @@ -0,0 +1,131 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Learn Lua by writing a "guess the number" game) +[#]: via: (https://opensource.com/article/20/12/lua-guess-number-game) +[#]: author: (Seth Kenlon https://opensource.com/users/seth) + +Learn Lua by writing a "guess the number" game +====== +Get to know Lua, a dynamically typed, lightweight, efficient, and +embeddable scripting language, by programming a simple game. +![Puzzle pieces coming together to form a computer screen][1] + +If you're a fan of scripting languages like Bash, Python, or Ruby, you might find Lua interesting. Lua is a dynamically typed, lightweight, efficient, and embeddable scripting language with an API to interface with C. It runs by interpreting bytecode with a register-based virtual machine, and it can be used for everything from procedural programming to functional programming to data-driven programming. It can even be used for object-oriented programming through the clever use of arrays, or _tables_, used to mimic classes. + +A great way to get a feel for a language is by writing a simple application you're already familiar with. Recently, some Opensource.com correspondents have demonstrated how to use their favorite languages to create a number-guessing game. [Lua][2] is one of my favorites, so here's my Lua version of the guessing game. + +### Install Lua + +If you're on Linux, you can install Lua from your distribution's software repository. On macOS, you can install Lua from [MacPorts][3] or [Homebrew][4]. On Windows, you can install Lua from [Chocolatey][5]. + +Once you have Lua installed, open your favorite text editor and get ready to code. + +### Lua code + +First, you must set up a pseudo-random number generator, so your player has something unpredictable to try to guess. This is a two-step process: first, you start a random seed based on the current time, and then you select a number within the range of 1 to 100: + + +``` +math.randomseed(os.[time][6]()) +number = math.random(1,100) +``` + +Next, create what Lua calls a _table_ to represent your player. A table is like an [array in Bash][7] or an ArrayList in Java. You can create a table and then assign child variables associated with that table. In this code, `player` is the table, and `player.guess` is an entry in that table: + + +``` +player = {} +player.guess = 0 +``` + +For the purpose of debugging, print the secret number. This isn't good for the game, but it's great for testing. Comments in Lua are preceded by double dashes: + + +``` +`print(number) --debug` +``` + +Next, set up a `while` loop that runs forever upon the condition that the value assigned to `player.guess` is not equal to the random `number` established at the start of the code. Currently, `player.guess` is set to 0, so it is not equal to `number`. Lua's math operator for inequality is `~=`, which is admittedly unique, but you get used to it after a while. + +The first thing that happens during this infinite loop is that the game prints a prompt so that the player understands the game. + +Next, Lua pauses and waits for the player to enter a guess. Lua reads from files and standard in (stdin) using the `io.read` function. You can assign the results of `io.read` to a variable that is dynamically created in the `player` table. The problem with the player's input is that it is read as a string, even if it's a number. You can convert this input to an integer type using the `tonumber()` function, assigning the result back to the `player.guess` variable that initially contained 0: + + +``` +while ( player.guess ~= number ) do +  print("Guess a number between 1 and 100") +  player.answer = io.read() +  player.guess = tonumber(player.answer) +``` + +Now that `player.guess` contains a new value, it's compared to the random number in an `if` statement. Lua uses the keywords `if`, `elseif`, and `else` and terminates the statement with the keyword `end:` + + +``` +  if ( player.guess > number ) then +    print("Too high") +  elseif ( player.guess < number) then +    print("Too low") +  else +    print("That's right!") +    os.[exit][8]() +  end +end +``` + +At the end, the function `os.exit()` closes the application upon success and the keyword `end` is used twice: once to end the `if` statement and again to end the `while` loop. + +### Run the application + +Run the game in a terminal: + + +``` +$ lua ./guess.lua +96 +Guess a number between 1 and 100 +1 +Too low +Guess a number between 1 and 100 +99 +Too high +Guess a number between 1 and 100 +96 +That's right! +``` + +That's it! + +### Intuitive and consistent + +As you may be able to tell from this code, Lua is sublimely consistent and fairly intuitive. Its table mechanism is a refreshing way of associating data, and its syntax is minimalistic and efficient. There are few wasted lines in Lua code; in fact, at least one pair of lines in this example could be optimized further, but I wanted to demonstrate data conversion as its own step (maybe you can find the two lines I'm referring to and restructure them). + +Lua is a pleasure to use, and its [documentation is a pleasure to read][9], mostly because there's just not that much to it. You'll learn the core language in no time, and then you'll be free to explore [LuaRocks][10] to discover all the great libraries others have contributed to make your time with Lua even easier. "Lua" means "moon" in Portuguese, so give it a try tonight. + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/20/12/lua-guess-number-game + +作者：[Seth Kenlon][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/seth +[b]: https://github.com/lujun9972 +[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/puzzle_computer_solve_fix_tool.png?itok=U0pH1uwj (Puzzle pieces coming together to form a computer screen) +[2]: https://www.lua.org/ +[3]: https://opensource.com/article/20/11/macports +[4]: https://opensource.com/article/20/6/homebrew-mac +[5]: https://opensource.com/article/20/3/chocolatey +[6]: http://www.opengroup.org/onlinepubs/009695399/functions/time.html +[7]: https://opensource.com/article/20/6/associative-arrays-bash +[8]: http://www.opengroup.org/onlinepubs/009695399/functions/exit.html +[9]: https://www.lua.org/docs.html +[10]: https://opensource.com/article/19/11/getting-started-luarocks