Worksheet1_ClassyFlasher.md

# Task 1:  Modifing Code to use Functions

Consider the following code

~~~c
DigitalOut led(LED1);

int main() {
    //Flash LED  5 times
	
	for (int x=0; x<5; x++){
		led != led;
		wait(0.5)
	}
	
	//Flash LED 10 times
	for (int x=0; x<5; x++){
		led != led;
		wait(0.5)
	}
~~~

First lets break this into a function. 
This would let us reuse the code in different places in the program.

The questions we need to ask:

  - What **chunks** of code are reused
  - What **variables** are in the reused code?
  - What **parameters** would we want to pass to the function?
  
The Reused code is the part in the loop

~~~c
	for (int x=0; x<5; x++){
		led != led;
		wait(0.5)
	}
~~~

In this example, the number of times we blink the LED is a good candidate for a parameter

## Function Definitions

Take for form **Return Type** **Funtion Name** (**parameters**)

  - **Return Type** we dont need to return anything, so *void* is good
  - **Function Name** Something sensible that descibes the functionaly
  - **Parameters** Number of times to **repeat** (an integer)
  
~~~c
void flash(int repeat){
   // Function Body goes here
 }
~~~

Therefore our function code ends up as

~~~
void flash(int repeat){
   for (int x=0; x< repeat; x++){
		led != led;
		wait(0.5);
   }
~~~

## Calling the Function

We can now call the function by using its name and supplying any parameters.

~~~c
int main() {
    //Flash LED  5 times
	flash(5);
	
	//Flash LED 10 times
	flash(10);
	}
~~~

## Your Task

 - Extend the function to take the delay time as a parameter.



# Task 2:  Getting Classy


To turn the function into a class we need to consider the attributes and functions.

I this case we have a couple of potential pataeters

 - **pin** electronic 'pin' the LED is connected to
 - **delay** how long to wait betwen toggling modes.
 
There are also candidates for functions

 - **flash** Actually do the blinking.
 
## Implementing the class

Standard CPP class definition,  note the use of initialisation list for the pin as it is an object.

~~~ c
#include "mbed.h"

class Flasher{
    private:
        float delay;
        DigitalOut pin;
        
  public:
     //Constructor
     Flasher(PinName thePin, float delayTime) : pin(thePin) {
         delay = delayTime;
	 }

	void flash(int times){
	    for (int x = 0; x< times; x++){
    		pin= !pin;
	    	wait(delay);
	    }
	}
};


int main() {
	//Setup
	Flasher ledOne = Flasher(LED1, 0.5);
	Flasher ledTwo = Flasher(LED2, 0.25);
	
	//Loop
	while(1){
		ledOne.flash(5);
		ledTwo.flash(10);
	}
}
~~~


## Task

 - Modify the Flasher class to take account of Multiple Lights.
 - Add functions for the State to the Flasher Class
 - If we have time, implement the button press to change state.
 
 
> NOTE: Each set of lights will work independently.  We need some form
> of multi tasking for both sets of lights to work together.  We will
> be looking at Concurrency over the next couple of days.