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> listOfNumbers = [1,4,99] [1,4,99] : List number > > listOfStrings = ["Hello","World"] ["Hello","World"] : List String > > emptyList = [] -- can be anything, we don't know yet [] : List a > Under the hood, List (linked list) is ...

> ourList = [1,2,3,4,5] [1,2,3,4,5] : List number > > firstElement = List.head ourList Just 1 : Maybe Int > > allButFirst = List.tail ourList Just [2,3,4,5] : Maybe (List Int) This wrapping into Maybe type happens because of the following scenario: What should List.head ret...

List.map : (a -> b) -> List a -> List b is a higher-order function that applies a one-parameter function to each element of a list, returning a new list with the modified values. import String ourList : List String ourList = ["wubba", "lubba", "dub",...

List.filter : (a -> Bool) -> List a -> List a is a higher-order function which takes a one-parameter function from any value to a boolean, and applies that function to every element of a given list, keeping only those elements for which the function returns True on. The function that List.f...

def multiply(factor: Int)(numberToBeMultiplied: Int): Int = factor * numberToBeMultiplied val multiplyBy3 = multiply(3)_ // resulting function signature Int => Int val multiplyBy10 = multiply(10)_ // resulting function signature Int => Int val sixFromCurriedCall = multiplyBy3(2) //6...

def numberOrCharacterSwitch(toggleNumber: Boolean)(number: Int)(character: Char): String = if (toggleNumber) number.toString else character.toString // need to explicitly specify the type of the parameter to be curried // resulting function signature Boolean => String val switchBetween3A...

def minus(left: Int, right: Int) = left - right val numberMinus5 = minus(_: Int, 5) val fiveMinusNumber = minus(5, _: Int) numberMinus5(7) // 2 fiveMinusNumber(7) // -2

To create a collection of n copies of some object x, use the fill method. This example creates a List, but this can work with other collections for which fill makes sense: // List.fill(n)(x) scala > List.fill(3)("Hello World") res0: List[String] = List(Hello World, Hello World, Hello...

While partial function are often used as convenient syntax for total functions, by including a final wildcard match (case _), in some methods, their partiality is key. One very common example in idiomatic Scala is the collect method, defined in the Scala collections library. Here, partial functions ...

Partial functions are very common in idiomatic Scala. They are often used for their convenient case-based syntax to define total functions over traits: sealed trait SuperType // `sealed` modifier allows inheritance within current build-unit only case object A extends SuperType case object B exten...

Some JavaScript engines (for example, the current version of Node.js and older versions of Chrome before Ignition+turbofan) don't run the optimizer on functions that contain a try/catch block. If you need to handle exceptions in performance-critical code, it can be faster in some cases to keep the ...

Use .slice() to extract substrings given two indices: var s = "0123456789abcdefg"; s.slice(0, 5); // "01234" s.slice(5, 6); // "5" Given one index, it will take from that index to the end of the string: s.slice(10); // "abcdefg"

Use .split to go from strings to an array of the split substrings: var s = "one, two, three, four, five" s.split(", "); // ["one", "two", "three", "four", "five"] Use the array method .join to go back to a string: s.split(&...

Flask lets you use templates for dynamic web page content. An example project structure for using templates is as follows: myproject/ /app/ /templates/ /index.html /views.py views.py: from flask import Flask, render_template app = Flask(__name__) @app...

This demonstrates how to print each element of a Map val map = Map(1 -> "a", 2 -> "b") for (number <- map) println(number) // prints (1,a), (2,b) for ((key, value) <- map) println(value) // prints a, b This demonstrates how to print each element of a list val l...

Full example code included at the end Windows components for OpenGL WGL WGL (can be pronounced wiggle) stands for "Windows-GL", as in "an interface between Windows and OpenGL" - a set of functions from the Windows API to communicate with OpenGL. WGL functions have a wgl prefix...

The Scala compiler will automatically convert methods into function values for the purpose of passing them into higher-order functions. object MyObject { def mapMethod(input: Int): String = { int.toString } } Seq(1, 2, 3).map(MyObject.mapMethod) // Seq("1", "2", &...

using System.Runtime.InteropServices; class PInvokeExample { [DllImport("user32.dll", CharSet = CharSet.Auto)] public static extern uint MessageBox(IntPtr hWnd, String text, String caption, int options); public static void test() { MessageBox(IntPtr.Zero,...

Arrays of simple type [DllImport("Example.dll")] static extern void SetArray( [MarshalAs(UnmanagedType.LPArray, SizeConst = 128)] byte[] data); Arrays of string [DllImport("Example.dll")] static extern void SetStrArray(string[] textLines);

If you want to check that a string contains only a certain set of characters, in this case a-z, A-Z and 0-9, you can do so like this, import re def is_allowed(string): characherRegex = re.compile(r'[^a-zA-Z0-9.]') string = characherRegex.search(string) return not bool(string) ...