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EP:20 - Domain Analysis

Part 20. Domain Analysis For interactive programs such as these, we will use the How to Design Worlds recipe. This is our guide for developing most interactive programs, in big-bang, these are called world programs. There are 2 parts when designing interactive programs, first is that we use pen and paper for the concept and then we then code the whole thing from our analysis. We are going to design the walking cat program using the recipe. The cat would start at the left edge of the display and walks across the screen. When it reaches the right side, it should just continue walking off screen The interactive part is that we can use the spacebar key to bring the cat back to the left side. There are 4 steps in domain analysis Sketch program scenarios Identify constant information Identify Changing information Identify big-bang options First we sketch program scenarios, we would need pen and paper for this one. These 2 or 3 images shows the states of t...
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EP: 19 - big-bang Mechanism

Part 19. big-bang We are using Dr. Racket to design interactive programs, from this day forward, this is going to be very complicated. Imagine we have 2 interactive programs, one that counts down from 10 to 0 and some animation of a cat walking in the screen. These programs are interactive by just pressing the space key, the program restarts. These interactive programs change state and it affects the program behavior. On the countdown program, it generates a number from 10 to 0 every 1 second. It is also the same with the cat program, it just changes the x coordinate of the cat every miliseconds. These are 2 different functions, now how can we combine these 2 functions. We combine them by using Dr. Rackets big-bang primitive. (big-bang 0           (on-tick next-cat)           (to-draw render-cat)) We use 0 as the initial world state, then on every tick, we get the next x coordinate, we pass it to the render c...
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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.  ...
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EP: 17 - HtDF with Enumeration

Part 17. HTDF with Enumeration In this example, We will be devising a function that gets the grade and bumps it to the next highest grade. Interesting thing about data definitions is that you do not have to make a data definition for each function. A data definition for that set of data can be reusable for any function that takes it as an input. Here we will define the signature, purpose and stub. Note that there is no grade above A. We will have to decide what happens to it. For now, there would be no change if we hit the highest grade. We need some examples. In enumerations, we should at least have as many tests as the total number of cases. We have 3 cases as defined by the definition. So we should have 3 tests. We can copy the template from the definition. This makes it easier. Note. The template must not contain any errors, this will affect our code when we implement them. Do not forget to change the template name to the actual function name ...
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EP: 16 - HtDF Interval Data Definition

Part 16. HtDF with Interval Data Definition We have defined the data definition for an interval, now we will make the function using HtDF recipe  The example asks us to make a function that produces true if the given seat number is an aisle For reference, look at the interpretation of data definition, it seems that seats 1 and 32 are aisle seats. Here we make the Signature, Purpose and Stub. Now we make the tests, When making tests for Intervals, include the first and last value and also the midpoints. Include also test for other points of variance across the interval.    Thanks to the Data definition provided, this helped us to create our test. HtDD and HtDF are related which can help us to design our functions. And finally, we just copy the template from the Data Definition, make sure you point that out. Comment out the stub and create the code. The function fulfills the requirements in the problem domain. Data definitions can help us define ...
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EP: 15 - Itemization Data Definition

Part 15. Itemization Data Definition The Itemization Data Definition is what we use for information compromised of 2 different categories, at least one of each is not a distinct value. This data definition is quite complex. As an example: Design a data definition for the current state of the countdown for the display, which falls in one of 3 categories. Not yet started from 10 to 1 seconds until midnight Complete This is like the countdown clock in TV. By looking at these states, the second one is not a distinct data value. Therefore this is not an enumeration. In this case, we will use the Itemization Data Definition. We have to choose a datatype that fulfills the categories. For someone that has done strict programming style method for a long time now, Data consisting of multiple data types confuse my brain, but I think Lisp Based languages tend to be liberal about the types of parameters unlike the C family or it's influences. This is one of the thing that lisp ...
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EP: 14 - Enumeration Data Definitions

EP. 14 - Enumeration Data Definitions Enumeration data definitions are used to represent information that has 2 or more distinct values. For example, We are designing a data definition for student grades. The grade can be A, B or C. In this problem domain, the grade can have 3 different values, which is A, B or C. Since we have a data which can have 3 distinct values, it makes sense that we use Enumeration for our template to make our data definitions. When making the Type Comment of the Enumeration Data Definition. We need to enumerate each distinct value.  When interpreting enumeration, this tends to be straightforward.  On enumerations, we do not need to have examples since they are redundant. The examples are already in our type comment. For the enumeration template, we need to make an if-conditions that would cover all the distinct values that we have here, in a Condition and the Corresponding expression.  Since the individual distinct value n...
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