To count all possible rectangles in a random grid requires a lot of scanning. My first thought was that the process would involve recursion. I wasn’t 100 percent certain, but I wanted to prep the code for such a possibility.
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Ever since I was a little boy and coded my first nested loop, I’ve enjoyed messing with grids in C. I’ve done monthly calendars in grids, rotated grids, manipulated grids mathematically — all sorts of fun girddy stuff. But I’m not done yet.
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Array notation involves the array’s name followed by a set of square brackets. Within these brackets is a reference to the array element’s number. It’s important to remember that the first element is zero. But the subscript need not always be a constant integer.
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I’m always mindful of the beginner when I write code for this blog. Even with my own code, I often go to pains to write things “the long way” just because I’m in the habit. Not every coder is so thoughtful. The reason is that C tends toward obfuscation. We must revel in this capability.
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You can’t just slap a data type upon a variable declared as void. No, a void type can be assigned a pointer. But even then, you can’t just typecast that pointer as an int and get away with it.
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The four standard data types in C programming are char, int, float, and double. A fifth type is void, which is used to declare storage of an unknown type. My goal is to see how badly I can abuse this data type.
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As with the select() function covered in last week’s Lesson, you can use other networking functions to scan for pending standard input while a program otherwise spins busy. The epoll() family of functions allow for such monitoring.
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A network program monitors one or more file descriptors (such as sockets) for activity. It reacts when information is ready to process. This technique can also be applied to keyboard input, though not as elegantly as the kbhit() function shown in last week’s Lesson.
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The C language is famously platform independent. This feature may seem unimportant these days, but back in the early computer era having a language you code code on multiple systems was key to the C language’s success. This benefit may be one reason why C lacks a specific function to check on the keyboard status to determine whether a key has been pressed. Such a function is hardware-dependent.
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Suppose you must write code that remains busy while checking to see whether a key has been pressed. The program repeats a loop, performing various tasks, but eager for that key press. When a key is pressed, the code fetches the key. Two things stand in your way to make this happen.
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