Tutorial by Examples

The exit construct can be used to pass a return code to the executing environment. #!/usr/bin/php if ($argv[1] === "bad") { exit(1); } else { exit(0); } By default an exit code of 0 will be returned if none is provided, i.e. exit is the same as exit(0). As exit is not a ...

The dict() constructor can be used to create dictionaries from keyword arguments, or from a single iterable of key-value pairs, or from a single dictionary and keyword arguments. dict(a=1, b=2, c=3) # {'a': 1, 'b': 2, 'c': 3} dict([('d', 4), ('e', 5), ('f', 6)]) # {'d': 4, 'e': ...

To create a simple C program which prints "Hello, World" on the screen, use a text editor to create a new file (e.g. hello.c — the file extension must be .c) containing the following source code: hello.c #include <stdio.h> int main(void) { puts("Hello, World")...

Operands of the abstract equality operator are compared after being converted to a common type. How this conversion happens is based on the specification of the operator: Specification for the == operator: 7.2.13 Abstract Equality Comparison The comparison x == y, where x and y are values, prod...

When both operands are numeric, they are compared normally: 1 < 2 // true 2 <= 2 // true 3 >= 5 // false true < false // false (implicitly converted to numbers, 1 > 0) When both operands are strings, they are compared lexicographically (according to alphabeti...

Operator != is the inverse of the == operator. Will return true if the operands aren't equal. The javascript engine will try and convert both operands to matching types if they aren't of the same type. Note: if the two operands have different internal references in memory, then false will be ret...

Alternatively, you can use the Interactive Ruby Shell (IRB) to immediately execute the Ruby statements you previously wrote in the Ruby file. Start an IRB session by typing: $ irb Then enter the following command: puts "Hello World" This results in the following console output (in...

Place this code in a file named HelloWorld.scala: object Hello { def main(args: Array[String]): Unit = { println("Hello World!") } } Live demo To compile it to bytecode that is executable by the JVM: $ scalac HelloWorld.scala To run it: $ scala Hello When the Scala...

The filter() method creates an array filled with all array elements that pass a test provided as a function. 5.1 [1, 2, 3, 4, 5].filter(function(value, index, arr) { return value > 2; }); 6 [1, 2, 3, 4, 5].filter(value => value > 2); Results in a new array: [3, 4, 5] Fi...

Program options can be handled with the getopt() function. It operates with a similar syntax to the POSIX getopt command, with additional support for GNU-style long options. #!/usr/bin/php // a single colon indicates the option takes a value // a double colon indicates the value may be omitted ...

Introduction HTML (Hypertext Markup Language) uses a markup system composed of elements which represent specific content. Markup means that with HTML you declare what is presented to a viewer, not how it is presented. Visual representations are defined by Cascading Style Sheets (CSS) and realized...

At the command line, first verify that you have Git installed: On all operating systems: git --version On UNIX-like operating systems: which git If nothing is returned, or the command is not recognized, you may have to install Git on your system by downloading and running the installer. See...

To iterate through a list you can use for: for x in ['one', 'two', 'three', 'four']: print(x) This will print out the elements of the list: one two three four The range function generates numbers which are also often used in a for loop. for x in range(1, 6): print(x) The res...

123.5.to_s #=> "123.5" String(123.5) #=> "123.5" Usually, String() will just call #to_s. Methods Kernel#sprintf and String#% behave similar to C: sprintf("%s", 123.5) #=> "123.5" "%s" % 123.5 #=> "123.5" "%d&quot...

"123.50".to_i #=> 123 Integer("123.50") #=> 123 A string will take the value of any integer at its start, but will not take integers from anywhere else: "123-foo".to_i # => 123 "foo-123".to_i # => 0 However, there is a difference when ...

"123.50".to_f #=> 123.5 Float("123.50") #=> 123.5 However, there is a difference when the string is not a valid Float: "something".to_f #=> 0.0 Float("something") # ArgumentError: invalid value for Float(): "something"

1/2 #=> 0 Since we are dividing two integers, the result is an integer. To solve this problem, we need to cast at least one of those to Float: 1.0 / 2 #=> 0.5 1.to_f / 2 #=> 0.5 1 / Float(2) #=> 0.5 Alternatively, fdiv may be used to return the floating point result of di...

#map, provided by Enumerable, creates an array by invoking a block on each element and collecting the results: [1, 2, 3].map { |i| i * 3 } # => [3, 6, 9] ['1', '2', '3', '4', '5'].map { |i| i.to_i } # => [1, 2, 3, 4, 5] The original array is not modified; a new array is returned conta...

The git clone command is used to copy an existing Git repository from a server to the local machine. For example, to clone a GitHub project: cd <path where you'd like the clone to create a directory> git clone https://github.com/username/projectname.git To clone a BitBucket project: cd ...

In its most simple form, an if condition can be used like this: var i = 0; if (i < 1) { console.log("i is smaller than 1"); } The condition i < 1 is evaluated, and if it evaluates to true the block that follows is executed. If it evaluates to false, the block is skipped....