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.<\/p>\n
As an example, consider the atoi()<\/em> function. Your task for this month’s Exercise is to write code that emulates the primary behavior of the atoi()<\/em> function: convert a string value to an integer.<\/p>\n Don’t worry about leading whitespace.<\/p>\n Don’t fret over a sign before the value (positive or negative).<\/p>\n And don’t frustrate yourself converting alphabetic characters.<\/p>\n In fact, here’s the programming skeleton to get you started:<\/p>\n Your task is to complete the convert()<\/em> function, which swallows a string value and returns a base 10 (decimal) integer. I can think of a number of ways to solve this Exercise. Click here<\/a> to view my solutions, but please try devising your own solution before peeking at what I’ve done.<\/p>\n","protected":false},"excerpt":{"rendered":" Sure, a function is available, but it’s good C programming practice to try writing your own. Continue reading
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\nAn older C language function, atoi()<\/em> converts a string to an integer value. The name implies “ASCII to Integer.” Its current implementation is as a macro for the strtol()<\/em> function. Both are prototyped in the stdlib.h<\/code> header.<\/p>\n\r\n#include <stdio.h>\r\n#include <stdlib.h>\r\n\r\nint convert(char *s)\r\n{\r\n return(r);\r\n}\r\n\r\nint main()\r\n{\r\n char value[] = \"345966\";\r\n int v;\r\n\r\n v = atoi(value);\r\n printf(\"%s from atoi() is %d\\n\",value,v);\r\n v = convert(value);\r\n printf(\"%s from convert() is %d\\n\",value,v);\r\n\r\n return(0);\r\n}<\/pre>\n