Lambda Functions

Key Ideas

• Lambda functions

Readings

Lambda Expressions

Lambda Expression in Java 8

Definition

Lambda functions are intended as a shorthand for defining functions that can come in handy to write concise code without wasting multiple lines defining a function. They are also known as anonymous functions, since they do not have a name unless assigned one. From What’s in a Lambda?

Definition

Interface - In its most common form, an interface is a group of related methods with empty bodies. The programmer is then responsible for writing the functions

Note

In most other languages, lambda functions do not need an interface and can be written as just as an anonmyous function. They all follow the same structure:

( ) -> { }

Lecture Code

/*

* Program: Lambda Examples
* Programmer: James Goudy

 */



// note that the interface can also be put in their own file
// note that a function is defined (which the programmer can name)
// in the interface.  The actual functin can then be written as 
// a global function or within a function.

interface InchtesToFeet{
    // Input is a double - inches
    // Output is a double executed by the function name "calculate"
    double calculate(double inches);
}

interface FtoC{
    // Input is a double - farh
    // Output is a double executed by the function name "calculate"
    double calculate(double farh);
    
}

interface GalaxayTip{
    // Input is nothing
    // Output is a string executed by the function name "calculate"   
    String run();
}

interface myFormula{
    // Input is two doubles
    // Output is a string executed by the function name "tabulate"      
    String tabulate(double num1,double num2);
    
}

public class Lambda_Lecture {
    
    //Global Lamda functions
    static InchtesToFeet itf =(i)->{return i/12.0;};
    static GalaxayTip  tip = ()->{return "Always bring a towel";};
    
    // multiple 2 numbers, add 50 then concantenate string
    // note this lambda function has multiple lines of code
    static myFormula mf = (n1,n2) ->{
        
        // define local variable
        double ans = 0;
        
        ans = n1* n2 + 50;
        
        return ans+ " units";
    };
    
    
    public static void main(String[] args) {
              
        int i = 36;
        double ft = 212;
        
        double xx = 10;
        double yy = 20;
        
        
        System.out.println(itf.calculate(i) + " feet");
        
        FtoC ftc = (f) -> {return (f-32.0) * 5.0/9.0;};
        System.out.println(ftc.calculate(ft) + " C");
        System.out.println(ftc.calculate(392.0) + " C");
        
        System.out.println(tip.run());
        
        System.out.println(mf.tabulate(xx, yy));     
        
    }
}

/*
3.0 feet
100.0 C
200.0 C
Always bring a towel
250.0 units
 */

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End of Topic