diff options
| -rw-r--r-- | bash.html.markdown | 4 | ||||
| -rw-r--r-- | kotlin.html.markdown | 73 | ||||
| -rw-r--r-- | pascal.html.markdown | 44 |
3 files changed, 117 insertions, 4 deletions
diff --git a/bash.html.markdown b/bash.html.markdown index be879538..cda877ad 100644 --- a/bash.html.markdown +++ b/bash.html.markdown @@ -228,10 +228,13 @@ mv s0urc3.txt dst.txt # sorry, l33t hackers... # Since bash works in the context of a current directory, you might want to # run your command in some other directory. We have cd for changing location: cd ~ # change to home directory +cd # also goes to home directory cd .. # go up one directory # (^^say, from /home/username/Downloads to /home/username) cd /home/username/Documents # change to specified directory cd ~/Documents/.. # still in home directory..isn't it?? +cd - # change to last directory +# => /home/username/Documents # Use subshells to work across directories (echo "First, I'm here: $PWD") && (cd someDir; echo "Then, I'm here: $PWD") @@ -256,6 +259,7 @@ print("#stderr", file=sys.stderr) for line in sys.stdin: print(line, file=sys.stdout) EOF +# Variables will be expanded if the first "EOF" is not quoted # Run the hello.py Python script with various stdin, stdout, and # stderr redirections: diff --git a/kotlin.html.markdown b/kotlin.html.markdown index 86d1baa0..6ff7c1dc 100644 --- a/kotlin.html.markdown +++ b/kotlin.html.markdown @@ -65,7 +65,7 @@ fun helloWorld(val name : String) { A template expression starts with a dollar sign ($). */ val fooTemplateString = "$fooString has ${fooString.length} characters" - println(fooTemplateString) // => My String Is Here! has 18 characters + println(fooTemplateString) // => My String Is Here! has 18 characters /* For a variable to hold null it must be explicitly specified as nullable. @@ -175,12 +175,12 @@ fun helloWorld(val name : String) { // Objects can be destructured into multiple variables. val (a, b, c) = fooCopy println("$a $b $c") // => 1 100 4 - + // destructuring in "for" loop for ((a, b, c) in listOf(fooData)) { println("$a $b $c") // => 1 100 4 } - + val mapData = mapOf("a" to 1, "b" to 2) // Map.Entry is destructurable as well for ((key, value) in mapData) { @@ -347,6 +347,8 @@ fun helloWorld(val name : String) { println(EnumExample.A) // => A println(ObjectExample.hello()) // => hello + + testOperator() } // Enum classes are similar to Java enum types. @@ -376,6 +378,71 @@ throws an exception if the value is null. */ var b: String? = "abc" val l = b!!.length + +/* You can add many custom operations using symbol like +, to particular instance +by overloading the built-in kotlin operator, using "operator" keyword + +below is the sample class to add some operator, and the most basic example +*/ +data class SomeClass(var savedValue: Int = 0) + +// instance += valueToAdd +operator fun SomeClass.plusAssign(valueToAdd: Int) { + this.savedValue += valueToAdd +} + +// -instance +operator fun SomeClass.unaryMinus() = SomeClass(-this.savedValue) + +// ++instance or instance++ +operator fun SomeClass.inc() = SomeClass(this.savedValue + 1) + +// instance * other +operator fun SomeClass.times(other: SomeClass) = + SomeClass(this.savedValue * other.savedValue) + +// an overload for multiply +operator fun SomeClass.times(value: Int) = SomeClass(this.savedValue * value) + +// other in instance +operator fun SomeClass.contains(other: SomeClass) = + other.savedValue == this.savedValue + +// instance[dummyIndex] = valueToSet +operator fun SomeClass.set(dummyIndex: Int, valueToSet: Int) { + this.savedValue = valueToSet + dummyIndex +} + +// instance() +operator fun SomeClass.invoke() { + println("instance invoked by invoker") +} + +/* return type must be Integer, +so that, it can be translated to "returned value" compareTo 0 + +for equality (==,!=) using operator will violates overloading equals function, +since it is already defined in Any class +*/ +operator fun SomeClass.compareTo(other: SomeClass) = + this.savedValue - other.savedValue + +fun testOperator() { + var x = SomeClass(4) + + println(x) // => "SomeClass(savedValue=4)" + x += 10 + println(x) // => "SomeClass(savedValue=14)" + println(-x) // => "SomeClass(savedValue=-14)" + println(++x) // => "SomeClass(savedValue=15)" + println(x * SomeClass(3)) // => "SomeClass(savedValue=45)" + println(x * 2) // => "SomeClass(savedValue=30)" + println(SomeClass(15) in x) // => true + x[2] = 10 + println(x) // => "SomeClass(savedValue=12)" + x() // => "instance invoked by invoker" + println(x >= 15) // => false +} ``` ### Further Reading diff --git a/pascal.html.markdown b/pascal.html.markdown index 6877afef..4144f900 100644 --- a/pascal.html.markdown +++ b/pascal.html.markdown @@ -3,6 +3,7 @@ language: Pascal filename: learnpascal.pas contributors: - ["Ganesha Danu", "http://github.com/blinfoldking"] + - ["Keith Miyake", "https://github.com/kaymmm"] --- @@ -92,5 +93,46 @@ End. ``` ```pascal +program Functional_Programming; -```
\ No newline at end of file +Var + i, dummy : integer; + +function factorial_recursion(const a: integer) : integer; +{ recursively calculates the factorial of integer parameter a } + +// Declare local variables within the function +// e.g.: +// Var +// local_a : integer; + +Begin + If a >= 1 Then + // return values from functions by assigning a value to the function name + factorial_recursion := a * factorial_recursion(a-1) + Else + factorial_recursion := 1; +End; // terminate a function using a semicolon after the End statement. + +procedure get_integer(var i : integer; dummy : integer); +{ get user input and store it in the integer parameter i. + parameters prefaced with 'var' are variable, meaning their value can change + outside of the parameter. Value parameters (without 'var') like 'dummy' are + static and changes made within the scope of the function/procedure do not + affect the variable passed as a parameter } + +Begin + write('Enter an integer: '); + readln(i); + dummy := 4; // dummy will not change value outside of the procedure +End; + +Begin // main program block + dummy := 3; + get_integer(i, dummy); + writeln(i, '! = ', factorial_recursion(i)); + // outputs i! + writeln('dummy = ', dummy); // always outputs '3' since dummy is unchanged. +End. + +``` |