Stop using the atoi() function! Yes, it’s a golden oldie, often my go-to function for converting strings to integers, but it’s weak. The strtol() function, on the other hand, not only converts strings to integers, it can validate input as well.
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This month’s Exercise is to emulate the antique atoi() function, which converts a string of digits into an integer value.
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Imagine my disappointment to learn that the atoi() function, one of the first I learned in C, is actually a macro. I’m horrified. As much as I treasure converting strings to integers, I shall survive this life-changing discovery.
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It’s not that programmers are lazy. Many professions involve a lot of copy-and-paste, borrowing stuff done before, re-purposing and re-using. Why re-invent the wheel? Still, doing so helps exercise your programming kung-fu as well as offers insights into how things work and why some operations are done the way they are.
As an example, consider the atoi() function.
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The C language lacks an exponentiation operator, which would raise a base value to a certain power. For example: 2^8, which in some programming languages is an expression to raise 2 to the 8th power. Instead, C uses the pow() function.
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Always be careful when manipulating strings! Tack on that null character, '\0', at the end of a string! And don’t worry about the C language string functions: They perform this important feature for you. But do they all?
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Say you must read 2048 bytes from a file. Which of the following fread() statements works for you: A, B, both, or neither?
A. c = fread( buffer, 2048, 1, fh);
B. c = fread( buffer, 1, 2048, fh);
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Like doing anything for a long period of time, I find myself often using the same approach to solving a programming puzzle. It’s habit. It’s tradition. And it often hinders my insight into the language.
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The key to making this month’s Exercise work isn’t to know when a word stops, but when the separator characters stop. That’s because words aren’t always separated by single characters.
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This month’s Exercise is based on code presented in the June 1 Lesson: split a string into separate words. The difference is that each word you pluck from the string is followed by the number of letters in that word.
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