From 126e82292e1ad0e06044fe1ed698567923d794a9 Mon Sep 17 00:00:00 2001 From: lkxed <39257389+lkxed@users.noreply.github.com> Date: Fri, 17 Jun 2022 19:30:01 +0800 Subject: [PATCH] =?UTF-8?q?=E4=BF=AE=E6=AD=A3=E4=BB=A3=E7=A0=81=E6=A0=BC?= =?UTF-8?q?=E5=BC=8F?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...et by writing a -guess the number- game.md | 44 +++++++++---------- 1 file changed, 20 insertions(+), 24 deletions(-) diff --git a/sources/tech/20210128 Start programming in Racket by writing a -guess the number- game.md b/sources/tech/20210128 Start programming in Racket by writing a -guess the number- game.md index 4f0bb194a6..7d672783b8 100644 --- a/sources/tech/20210128 Start programming in Racket by writing a -guess the number- game.md +++ b/sources/tech/20210128 Start programming in Racket by writing a -guess the number- game.md @@ -1,21 +1,21 @@ -[#]: collector: (lujun9972) -[#]: translator: ( ) -[#]: reviewer: ( ) -[#]: publisher: ( ) -[#]: url: ( ) -[#]: subject: (Start programming in Racket by writing a "guess the number" game) -[#]: via: (https://opensource.com/article/21/1/racket-guess-number) -[#]: author: (Cristiano L. Fontana https://opensource.com/users/cristianofontana) +[#]: subject: "Start programming in Racket by writing a "guess the number" game" +[#]: via: "https://opensource.com/article/21/1/racket-guess-number" +[#]: author: "Cristiano L. Fontana https://opensource.com/users/cristianofontana" +[#]: collector: "lkxed" +[#]: translator: " " +[#]: reviewer: " " +[#]: publisher: " " +[#]: url: " " Start programming in Racket by writing a "guess the number" game ====== -Racket is a great way to learn a language from the Scheme and Lisp -families. +Racket is a great way to learn a language from the Scheme and Lisp families. + ![Person using a laptop][1] I am a big advocate of learning multiple programming languages. That's mostly because I tend to get bored with the languages I use the most. It also teaches me new and interesting ways to approach programming. -Writing the same program in multiple languages is a good way to learn their differences and similarities. Previously, I wrote articles showing the same sample data plotting program written in [C & C++][2], JavaScript with [Node.js][3], and [Python and Octave][4]. +Writing the same program in multiple languages is a good way to learn their differences and similarities. Previously, I wrote articles showing the same sample data plotting program written in [C & C++][2], JavaScript with [Node.js][3], and [Python and Octave][4]. This article is part of another series about writing a "guess the number" game in different programming languages. In this game, the computer picks a number between one and 100 and asks you to guess it. The program loops until you make a correct guess. @@ -31,7 +31,6 @@ When I start learning a new language, I usually look for a tutorial that introdu Starting with Racket makes sense because it is very mature and versatile, and the community is very active. Since Racket is a Lisp-like language, a major characteristic is that it uses the [prefix notation][9] and a [lot of parentheses][10]. Functions and operators are applied to a list of operands by prefixing them: - ``` (function-name operand operand ...) @@ -58,15 +57,14 @@ The major Linux distributions offer packaged versions of Racket, so [installatio Here is a version of the "guess the number" program written in Racket: - ``` #lang racket (define (inquire-user number)   (display "Insert a number: ") -  (define guess (string->number (read-line))) -  (cond [(> number guess) (displayln "Too low") (inquire-user number)] -        [(< number guess) (displayln "Too high") (inquire-user number)] +  (define guess (string->number (read-line))) +  (cond [(> number guess) (displayln "Too low") (inquire-user number)] +        [(< number guess) (displayln "Too high") (inquire-user number)]         [else (displayln "Correct!")])) (displayln "Guess a number between 1 and 100") @@ -75,14 +73,12 @@ Here is a version of the "guess the number" program written in Racket: Save this listing to a file called `guess.rkt` and run it: - ``` -`$ racket guess.rkt` +$ racket guess.rkt ``` Here is some example output: - ``` Guess a number between 1 and 100 Insert a number: 90 @@ -111,9 +107,9 @@ Now for the next line. `(define ...)` is used to declare new variables or functi This function recursively calls itself to repeat the question until the user guesses the right number. Note that I am not using loops; I feel that Racket programmers do not like loops and only use recursive functions. This approach is idiomatic to Racket, but if you prefer, [loops are an option][18]. -The first step of the `inquire-user` function asks the user to insert a number by writing that string to the console. Then it defines a variable called `guess` that contains whatever the user entered. The [`read-line` function][19] returns the user input as a string. The string is then converted to a number with the [`string->number` function][20]. After the variable definition, the [`cond` function][21] accepts a series of conditions. If a condition is satisfied, it executes the code inside that condition. These conditions, `(> number guess)` and `(< number guess)`, are followed by two functions: a `displayln` that gives clues to the user and a `inquire-user` call. The function calls itself again when the user does not guess the right number. The `else` clause executes when the two conditions are not met, i.e., the user enters the correct number. The program's guts are this `inquire-user` function. +The first step of the `inquire-user` function asks the user to insert a number by writing that string to the console. Then it defines a variable called `guess` that contains whatever the user entered. The [read-line function][19] returns the user input as a string. The string is then converted to a number with the [string->number function][20]. After the variable definition, the [cond function][21] accepts a series of conditions. If a condition is satisfied, it executes the code inside that condition. These conditions, `(> number guess)` and `(< number guess)`, are followed by two functions: a `displayln` that gives clues to the user and a `inquire-user` call. The function calls itself again when the user does not guess the right number. The `else` clause executes when the two conditions are not met, i.e., the user enters the correct number. The program's guts are this `inquire-user` function. -However, the function still needs to be called! First, the program asks the user to guess a number between 1 and 100, and then it calls the `inquire-user` function with a random number. The random number is generated with the [`random` function][22]. You need to inform the function that you want to generate a number between 1 and 100, but the `random` function generates integer numbers up to `max-1`, so I used 101. +However, the function still needs to be called! First, the program asks the user to guess a number between 1 and 100, and then it calls the `inquire-user` function with a random number. The random number is generated with the [random function][22]. You need to inform the function that you want to generate a number between 1 and 100, but the `random` function generates integer numbers up to `max-1`, so I used 101. ### Try Racket @@ -124,15 +120,15 @@ Learning new languages is fun! I am a big advocate of programming languages poly via: https://opensource.com/article/21/1/racket-guess-number 作者：[Cristiano L. Fontana][a] -选题：[lujun9972][b] +选题：[lkxed][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/cristianofontana -[b]: https://github.com/lujun9972 -[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/laptop_screen_desk_work_chat_text.png?itok=UXqIDRDD (Person using a laptop) +[b]: https://github.com/lkxed +[1]: https://opensource.com/sites/default/files/lead-images/laptop_screen_desk_work_chat_text.png [2]: https://opensource.com/article/20/2/c-data-science [3]: https://opensource.com/article/20/6/data-science-nodejs [4]: https://opensource.com/article/20/2/python-gnu-octave-data-science