Created
October 12, 2019 02:19
-
-
Save kirkdrichardson/8608f4b406d6fbd4504f9a328aa7b044 to your computer and use it in GitHub Desktop.
Basic Functional Programming in Dart
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| // Basic Functional Programming in Dart (as of v2.5) | |
| // See live at https://dartpad.dartlang.org/8608f4b406d6fbd4504f9a328aa7b044 | |
| void main() { | |
| // Functions are objects | |
| print('-----------------ANONYMOUS (LAMBDA) FUNCTIONS--------------------'); | |
| // Here we assign an anonymous fx to a variable. | |
| Function squareANumber = (int num) { | |
| return num*num; | |
| }; | |
| // This is an equivalent anonymous, or "lambda" fx, using the fat arrow syntax. | |
| Function square = (int num) => num*num; | |
| // Call as you would a regular class method. | |
| print(squareANumber(4)); | |
| print(square(4)); | |
| print('-----------------HIGHER ORDER FUNCTIONS--------------------'); | |
| // i.e., a function that | |
| // A) accepts a function, OR | |
| // B) returns a function, OR | |
| // C) both accepts and returns a function | |
| // A) accepts a function | |
| String modifyString(String str, Function modifier) { | |
| return modifier(str); | |
| } | |
| String modifiedString = modifyString('Hello', (String str) => str + ' World'); | |
| print(modifiedString); | |
| // B) returns a function | |
| Function getStringModifierForType(String str) { | |
| if (str.length < 10) { | |
| return () => print('$str is too short'); | |
| } | |
| return () => print('$str is too long'); | |
| } | |
| // Build appropriate function based on string length | |
| Function conditionalStringModifier = getStringModifierForType('Hello'); | |
| // Call returned function. | |
| conditionalStringModifier(); | |
| // Reassign using different argument | |
| conditionalStringModifier = getStringModifierForType('Hello World'); | |
| // Call returned function | |
| conditionalStringModifier(); | |
| print('-----------------CLOSURES--------------------'); | |
| // Closure is a special fx in which you can mutate / modify variables present in parent scope variables | |
| // i.e., it is about scope, e.g. | |
| // A) a function that has access to parent scope | |
| String variableInParentScope = 'You'; | |
| Function myLambdaFunctionClosure = () { | |
| variableInParentScope += ' Rock!!!'; | |
| }; | |
| // we are able not modify variables in the parent scope, so be careful! | |
| myLambdaFunctionClosure(); | |
| print(variableInParentScope); | |
| // B) a function that has access to variables in its lexical scope, even when invoked outside of its original scope | |
| Function myFunctionReturningClosure = () { | |
| String lexicalScopeVariable = 'No more'; | |
| Function innerFunction = () { | |
| return lexicalScopeVariable + ' Bad Days :)'; | |
| }; | |
| return innerFunction; | |
| }; | |
| // Now we can get that inner function, that forms a closure around that lexically scoped variable: | |
| Function returnedFunction = myFunctionReturningClosure(); | |
| // Then we can call the returned fx to extract the value | |
| String valueReturned = returnedFunction(); | |
| print(valueReturned); | |
| // Or, we can roll all of that up like this: | |
| print(myFunctionReturningClosure()()); | |
| } |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment