Introduction to Perl 6 Documentation

Transcription

1 Introduction to Perl 6 Documentation Release Suman Khanal and Ashish Khanal Oct 05, 2018

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3 Contents 1 Introduction 3 2 Running Perl 6 notebook Docker way Perl 6 Basics: Running the program Running in the terminal Running in Docker container Running in Atom IDE Running in VS Code Practical Examples 13 5 Variables and scope Variable names Functions/Subroutines 17 7 Loops, conditionals, and recursion 19 8 Iteration 21 9 Strings Arrays and Lists Hashes Classes and Objects Regexes and Grammars Functional Programming Creating Perl 6 modules Example Exercises Question i

4 16.2 Question Question Indices and tables 39 ii

5 Contents: Contents 1

6 2 Contents

7 CHAPTER 1 Introduction Perl 6 is a member of the Perl family of programming languages. While historically several interpreter and compiler implementations were being written, today only the Rakudo Perl 6 implementation is in active development. It is introducing elements of many modern and historical languages. Compatibility with Perl 5 is not a goal, though a compatibility mode is part of the specification. See Perl 6 website here. For Wikipedia reference and overview see here. 3

8 4 Chapter 1. Introduction

9 CHAPTER 2 Running Perl 6 notebook As I am more familiar with Docker, I am explaining the docker way of running Perl 6 notebook. Of course there are other ways to achieve the same. 2.1 Docker way Step 1: Docker installation To run Perl 6 notebook, first install Docker in your respective operating system. As I am running Windows, I install Docker from here. Go to your docker terminal and find ip-address as shown in this figure: 5

10 2.1.2 Step 2: Pulling the Docker image with Perl 6 kernel From the docker terminal, pull the image with command: docker pull sumdoc/perl-6-notebook Step 3: Running the container In the docker terminal, type: docker run -it -p 8888:8888 sumdoc/perl-6-notebook. Note the token number Step 4: Accessing the running container Open your web browser and type: ip-address:8888. In my case, I type: as my ip-address is: You will be greeted with such window: 6 Chapter 2. Running Perl 6 notebook

11 2.1.5 Step 5: Login with token number After inserting the token number(which is shown above), you will get such webpage: On the right upper corner, you will find New button. Click on that and you will get Perl 6 as option. Click on Perl 6. After that you will have this Perl 6 notebook running Docker way 7

12 2.1.6 Step 6: Mounting the host folder into docker folder You may be having Perl 6 files or Perl 6 notebooks (that is.ipynb files) in a folder in your PC that you want to work inside docker. In that case you have to mount that folder inside docker. Here I will give one example. I have my Perl 6 files in a folder (Note I am in Windows 10) named C:\Users\Suman\Desktop\Perl6 in my host and mounting on /tmp folder inside docker with the command docker run -it -p 8888:8888 -v /c/users/suman/desktop/perl6:/tmp sumdoc/perl-6-notebook which is clearly shown in figure below: Step 7: Accessing the Perl 6 files of the host After following above instructions and inserting the token number you will reach the notebook page. Find the folder where you mounted your host folder. In my case I mounted on /tmp. 8 Chapter 2. Running Perl 6 notebook

13 Now click on that /tmp folder and you will find your Perl 6 files. Then if you want to open your Perl 6 notebook, click the respective.ipynb file. Happy coding in Perl 6!! 2.1. Docker way 9

14 10 Chapter 2. Running Perl 6 notebook

15 CHAPTER 3 Perl 6 Basics: Running the program Perl 6 programs can be run in The terminal or The docker container or The Atom editor with Perl 6 plugin installed or The Visual Studio Code with Code Runner installed 3.1 Running in the terminal Make sure Perl 6 binary is in your path. Lets see an example how we can run perl 6 programs: 1 say "Hello World!" Save the above program in hello.p6 file and run in the terminal by typing: perl6 hello.p6. You will see the output Hello World!. Congratulations for running your first perl 6 program!! Other programs can be run similarly. 3.2 Running in Docker container It is the most versatile way of running Perl 6 programs independent of OS. After installing Docker ToolBox, go to interactive shell, then pull and run the Perl-6 image from DockerHub. Here is one example: docker run -it -v $PWD:/tmp sumdoc/perl-6 bash This command runs the sumdoc/perl-6 image interactively, at the same time mounts the $PWD inside /tmp folder of the container where you will see the same files as contained in $PWD. Inside /tmp directory, run your scripts with command perl6 <program>.p6 For more information and running notebooks, see here. 11

16 3.3 Running in Atom IDE For running.p6 programs in Atom IDE, make sure the plugin is installed and Perl6 binary is in your path. After that, simply use the Ctrl+Shift+B keyboard shortcut that runs your program. Atom is easier to use and can be highly customised. 3.4 Running in VS Code For running.p6 programs in VS Code, make sure the Code Runner plugin is installed and Perl6 binary is in your path. After that, use keyboard shortcut Ctrl+Alt+N to run the program. 12 Chapter 3. Perl 6 Basics: Running the program

17 CHAPTER 4 Practical Examples Following codes may be unoptimised version, but shows how it is implemented for beginners. This example shows the number of elements that contain digit 7 only twice in a range starting from 0 to num in Perl 6. 1 sub count($num) { 2 3 for 0..$num -> $v { 4 if $v.str.indices("7")==2 { 6 } 7 } 8 9 } print count(99999) Same case implemented in Python 3 in exactly the same way. Here s the code. 1 def count(num): 2 lst=[] 3 for i in range(num): 4 if str(i).count("7")==2: 5 lst.append(i) 6 return len(lst) 7 8 print(count(99999)) 13

18 14 Chapter 4. Practical Examples

19 CHAPTER 5 Variables and scope A variable is a container that has a name and holds a value. An assignment statement uses the equals sign = and gives a value to a variable, but, before you can assign a value to a variable, you first need to create the variable by declaring it (if it does not already exist): 1 > my $message; # variable declaration, no value yet 2 > $message = 'And now for something completely different'; 3 And now for something completely different 4 > my $number = 42; # variable declaration and assignment > $number = 17; # new assignment 7 17 In Perl 6, variable names start with a so-called sigil, i.e., a special non-alphanumeric character such as %, &, and some others. The keyword my is a way of declaring a new variable. Whenever you create a new variable in Perl, you need to declare it, i.e., tell Perl that you re going to use that new variable; this is most commonly done with the my keyword, which declares a lexical variable. 5.1 Variable names Variable names can be as long as you like. They can contain both letters and numbers, but user-defined variable names can t begin with a number. Variable names are case-sensitive, i.e., $message is not the same variable as $Message or $MESSAGE. It is legal to use uppercase letters, but it is conventional to use only lower case for most variables names. Some people nonetheless like to use $TitleCase for their variables or even pure $UPPERCASE for some special variables. Unlike most other programming languages, Perl 6 does not require the letters and digits used in variable names to be plain ASCII. You can use all kinds of Unicode letters which can be useful for non-english programmers (provided that these Unicode characters are handled correctly by your text editor and your screen configuration). 15

20 16 Chapter 5. Variables and scope

21 CHAPTER 6 Functions/Subroutines 17

22 18 Chapter 6. Functions/Subroutines

23 CHAPTER 7 Loops, conditionals, and recursion 19

24 20 Chapter 7. Loops, conditionals, and recursion

25 CHAPTER 8 Iteration 21

26 22 Chapter 8. Iteration

27 CHAPTER 9 Strings 23

28 24 Chapter 9. Strings

29 CHAPTER 10 Arrays and Lists 25

30 26 Chapter 10. Arrays and Lists

31 CHAPTER 11 Hashes 27

32 28 Chapter 11. Hashes

33 CHAPTER 12 Classes and Objects 29

34 30 Chapter 12. Classes and Objects

35 CHAPTER 13 Regexes and Grammars 31

36 32 Chapter 13. Regexes and Grammars

37 CHAPTER 14 Functional Programming 33

38 34 Chapter 14. Functional Programming

39 CHAPTER 15 Creating Perl 6 modules A module is usually a source file or set of source files that expose Perl 6 constructs. These are typically packages (classes, roles, grammars), subroutines, and sometimes variables. Module distributions (in the set of related source files sense) in Perl 6 have the same structure as any distribution in the Perl family of languages: there is a main project directory containing a README and a LICENSE file, a lib directory for the source files, which may be individually referred to as modules and/or may themselves define modules with the module keyword, a t directory for tests, and possibly a bin directory for executable programs and scripts. Source files generally use the.pm6 extension, and scripts or executables use the.p6. Test files use the.t extension. Files which contain documentation use the.pod6 extension. Creating modules has become easier with App:Mi6 package. To use this tool, first get it installed with command: zef install App::Mi6 Or you can use this docker image directly. App::Mi6 is a minimal authoring tool for Perl 6. Features are: Create minimal distribution skeleton for Perl 6 Generate README.md from lib/main/module.pm6 s pod Run tests by mi6 test Release your distribution tarball to CPAN Function mi6 new Foo::Bar mi6 build mi6 test mi6 release Table 1: Few App::Mi6 functions Use Create Foo-Bar distribution Build the distribution and re-generate README.md/META6.json Run tests Release your distribution to CPAN 35

40 15.1 Example When you run mi6 new Foo::Bar in terminal, it will create directory Foo-Bar inside which following files and directories will be found: lib directory contains source files bin directory for executable programs and scripts t directory for tests. Test files use the.t extension META6.json containing metadata README.md file which is a markdown-formatted text file, which will later be automatically rendered as HTML by GitHub LICENSE file.travis.yml file for continuous integration dist.ini file to customise mi6 behavior 36 Chapter 15. Creating Perl 6 modules

41 CHAPTER 16 Exercises 16.1 Question The Collatz Conjecture: The Collatz Conjecture, named after Lothar Collatz, states that, starting from any natural number, it is possible to reach 1 by following certain rules: 1. Take n: If n is odd, set n = 3n+1. Else, if n is even, set n = n/2. 2. Repeat the procedure until 1 is reached. The conjecture is currently unproven, although it has been shown to hold for numbers up to Starting with the above code, make a program that takes as command-line input a single number, representing a number of Collatz steps (steps required to reach 1 by following the Collatz procedure), and computes the lowest number (starting from 1) which requires this number of Collatz steps. For example, if the number input was 949, your program should output 63,728,127; similarly, if you input 1132, it should output 9,780,657,630 as the lowest number requiring 1132 Collatz steps. Since these are fairly large numbers, and it might take your code a very long time to reach them (unless you use a more advanced technique, such as in some manner memoizing previous results and efficiently checking to see if you ve already found the number of steps remaining from a given number - but I digress) you can use the following smaller test cases: For an input of 6, your code should output 10. For an input of 45, it should output 361. Finally, for an input of 260, it should print Question 2 Implement a function, increment that takes as input a vector of integers and returns a new vector of integers that has the values of the original list each incremented by one. For example: [1,2,3] > [2,3,4] 37

42 16.3 Question 3 Implement a function, incrementmut that takes as input a vector of integers and modifies the values of the original list by incrementing each value by one. For example: [1,2,3] > [2,3,4] 38 Chapter 16. Exercises

43 CHAPTER 17 Indices and tables genindex modindex search 39