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EP: 18 - HtDF with Itemization

Part 18. HtDF with Itemization

From the Countdown Display definition that we have made earlier, we are going to make a function out of it.

We have to output an image depending on the state of the countdown. 

Here is the Signature, Purpose and Stub.

It is recommended to run the code often, the earlier we detect bugs, the better.

We need some examples. For tests on itemizations, we need to have as many tests as there are cases. Also, if we have an interval, we have to test points of variance.

For the Interval, there is not much variance in the seconds before midnight so it is okay to have only one test for that.

There is a primitive called text which converts text to an image, we can also use number->string to convert a number into a string datatype.

Note that when we are devising tests, we are already working out the behavior of the function before we start coding.

Now we get the template and start creating the function body. 


The benefit of using a template is that we can immediately code the body of the function using the tests.

The data definition told us that there are 3 cases. It helps us made the function easier.

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