06-02. Rainfall

This is a simple rainfall analysis programme that counts the number of days with no rain from the data it supplied.

Let's set up the boilerplate.

As we're going to use a list to store the rainfall data, we need to tell C we're using the System Collections generic library of commands.

In our main programme section, we'll have a list of double numbers.

Remember, that's numbers with decimal places called dailyrainfallmm We'll tell C this is a new list of double numbers and enumerate the list with some data inside curly brackets.

Of course, in a real application it would be reading this data from the rainfall sensor's memory.

These numbers are millimetres of rain in a day, and we've collected 14 days worth of data.

Next, we'll output two messages information for the user and then days with no rain concatenated to the return value from a function we'll write in a moment called Analysis 1, which will require the data from our daily rainfall list.

We're going to write this programme in two ways.

So we'll repeat that bit of code, but this time using the analysis to function that we'll write in a moment.

Okay, so define the analysis 1 function in the subprogram section.

This will return a double number and require some data.

So we'll call the parameter data, which will be our list of double numbers.

Note how the values from daily rainfallmm are parsed into this new list.

We could have used a global list instead, but this is a better way of writing the programme.

The count of the number of days with no rainfall is stored in a variable identified as count.

That will also be a double number.

But thinking about it, we maybe should have used an integer here.

we'll initialise that to zero.

Now we want to iterate through all the elements in data.

Here's another use for the for loop.

For each double value in data, if value is the same as zero, then add one to count.

Finally, outside of the loop, return the value of count back to the main programme.

Hopefully you can see how useful a for loop is.

Here.

The statement almost reads as it would in English.

For each double value in data, if there was no rain, add one to the daily count.

So in the subprogram you can see how it's possible to iterate through all the elements in a list or an array using a for loop, but without referring to the index.

However, let's write the same subprogram that way too, so you can see the difference, even though the output will be the same.

Here's a second function called analysis2.

It's the same as analysis1, except when we get to the for loop, we will use the index instead.

You can see it's slightly more complicated when we iterate by index compared to iterating by element.

This is really common in programming.

There are hundreds of ways to write the same programme.

There's often not a correct answer.

If it works, it works.

However, we usually want the most efficient solution in terms of readability of the code for humans.

So in this case, analysis 1 is easier to understand in terms of efficiency of execution and memory footprint.

Both of these solutions are pretty much the same.

Once the code is compiled, let's run the programme and we can see the same output from both subprograms.