Someone kindly help me figure out the function of COUNTER in this program!!!

Question

1.00/5 (4 votes)

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double gallons, liters;
int counter;

counter =0;

for(gallons=1; gallons<=10; gallons++)
{
   liters=gallons*3.7;
   System.out.println(gallons + " gallons is equal to " + liters +  "liters");

   counter++;

   if(counter==2)
   {
      System.out.println();

      counter=0;
   }
}

Posted 31-Jul-15 2:31am

anaQata

Updated 31-Jul-15 3:06am

Andy Lanng

v2

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Comments

Michael_Davies 31-Jul-15 8:42am

Looks like someone wanted a blank line after every two lines.

anaQata 31-Jul-15 8:56am

yeah. I do get that.
I wanted someone to explain to me the logic behind it!!

[no name] 31-Jul-15 9:21am

You want someone to explain your own logic to you?

F-ES Sitecore 31-Jul-15 9:22am

Someone who doesn't know about modulus.

anaQata 31-Jul-15 9:25am

i saw the code somewhere. Its not my original...Wes

3 solutions

Solution 1

Quote:
I wanted someone to explain to me the logic behind it!!

That could easily achieved by code inspection, that is mentally simulating the code execution.

At startup counter is equal to 0.
At first iteration (after first output line) it gets incremented, beocming 1, hence the if block is not entered.
At second iteration (after th output line) it get incremented again, becoming 2. Now the if block is entered, the newline is printed and counter becomes 0 again. This repeats over and over.

Posted 31-Jul-15 3:06am

CPallini

Comments

anaQata 31-Jul-15 9:32am

Thank you very much CPallini. Aren't you supposed to EXPLICITLY show that the counter is linked to the for loop?

CPallini 31-Jul-15 11:08am

Actually counter isn't neeeded at all, you may use the loop index, instead:
if (gallons % 2 == 0)
{
//...
}

Solution 3

The debugger is your friend.

For problems like understanding how a program works, there is nothing like the debugger. The debugger let you see the execution step by step and this is invaluable.

The debugger is your friend too when it comes to understanding why a program don't do what you want.

Posted 31-Jul-15 6:36am

Patrice T

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Andy Lanng · Accepted Answer · 2015-07-31T03:15:00

I fixed the line indent.

It's not well done, but it makes sense from a requirement point of view. Requirements are arbitrary so 'logic' doesn't come in to the decision.

The code will increment gallons in each loop.
liters will be gallons times 3.7
the output is printed
every even number of gallons gets a new line under it.

Output will be:

1 gallons is equal to 3.7 liters
2 gallons is equal to 7.4 liters

3 gallons is equal to 11.1 liters
4 gallons is equal to 14.8 liters

5 gallons is equal to 18.5 liters
6 gallons is equal to 22.2 liters

7 gallons is equal to 25.9 liters
8 gallons is equal to 29.6 liters

9 gallons is equal to 33.3 liters
10 gallons is equal to 37 liters

C#

double gallons, liters;
int counter; // there is no reason not to join this line with the next
counter =0;  // but there is no need for a counter

// this is a for loop: (init;limit;increment)
for(gallons=1; gallons<=10; gallons++)
{
   liters=gallons*3.7;
   System.out.println(gallons + " gallons is equal to " + liters +  "liters");

   counter++;
   if(counter==2)
   {
      System.out.println();
      counter=0;
   }

   // the alternative excluding the counter is:
   //if(gallons % 2 == 0)
   //   System.out.println();
}

This is how I would have written it:

C#

for(int counter = 1; counter <= 10; counter ++)
{
   double gallons = counter; 
   double liters = gallons * 3.7;
   System.out.println(gallons + " gallons is equal to " + liters +  "liters");

   if(counter % 2 == 0)
      System.out.println();
}

So now counter is defined only by the for loop. The two are inseparable. The value of counter is explicitly tied to the for loop.

The gallons and liters variables also only exist in the scope of the for loop, but there value is implicitly connected to the loop. They are not defined by, nor do they define the for loop.

We could consider the doubles as explicit as they are defined by the counter, which is defined by the loop, but that's letting semantics get in the way of terminology.