The goal of the November 2018 Exercise on this blog was to count in “alphabedecimal,” or base 26 using the uppercase letters of the alphabet. The solution cycles from AAAA to ZZZZ flipping each character (or digit) one at a time, just as numbers are counted. The challenge is to do so without employing a nested loop.
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System errors happen. Your program accesses the operating system and . . . something goes wrong. When it does, the function returns -1 and your code must rely upon our old buddy errno to discover what went wrong and possibly output an informative error message.
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There’s a scene in the HBO series Silicon Valley that aptly describes a magic number in programming code: Coders are trying to figure out a compression algorithm and they encounter a large integer value. They wonder what it means; it’s not commented or assigned to a clever constant name. It’s just . . . a magic number.
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In my code, in my books, and in my online courses, I typecast the malloc() function. This is something I’ve done for a while, but never really knew why — until now. I’ve also learned that doing so is considered “bad programming practice” by some in the C community.
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For this month’s Exercise, my solution to the scramble() function requires a second array. You could code a scramble() function without using a second array (or storage buffer), swapping individual characters within the string, but I chose not to.
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Passing a string to a function? Check!
Passing an array of strings to a function? Watch out!
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Most functions are nice to strings. They manipulate the characters in a useful or clever way, returning an important value or an updated version of the text. But not every string function needs to be so kind, such as the one you write for this Exercise.
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You have two choices when modifying a string in a function: You can modify the string directly or you can create a new string and return it. Either way, a new string is created based on the old.
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Despite teaching the C language, I still find myself at odds with pointers. Specifically, it’s the double pointers that remind me of my mortality. I found myself getting into the double pointer polka recently when I tried to work with an array of strings, passing each one individually to a function. O! The pain!
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I enjoy it when an experienced coder reviews my stuff. I’m happy with the feedback, and occasionally they toss me a bone. This time it was a rather obscure bone, but I see the point: Avoid using negative array elements.
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