{"id":2737,"date":"2017-10-08T00:01:40","date_gmt":"2017-10-08T07:01:40","guid":{"rendered":"http:\/\/c-for-dummies.com\/blog\/?p=2737"},"modified":"2017-10-07T11:09:53","modified_gmt":"2017-10-07T18:09:53","slug":"right-string-solution","status":"publish","type":"post","link":"https:\/\/c-for-dummies.com\/blog\/?p=2737","title":{"rendered":"Right String – Solution"},"content":{"rendered":"

For this month’s Exercise<\/a>, I offer both a string function solution as well as a solution that uses pointers. As you can guess, I thought of the string method first, which is where most programmers would run to avoid the dratted topic of pointers.
\n
\nThe same right()<\/em> function declaration is used for both examples:<\/p>\n

char *right(char *string, int size)<\/code><\/p>\n

The text string<\/code> is passed to the function. Variable size<\/code> determines how many characters from the right side of string<\/code> are returned, though technically a pointer to the start of that chunk is what’s returned.<\/p>\n

For my non-pointer version, I crafted the following right()<\/em> function:<\/p>\n

\r\nchar *right(char *string, int size)\r\n{\r\n    int len;\r\n\r\n    len = strlen(string);\r\n    return(string+len-size-1);\r\n}<\/pre>\n
Variable len<\/code> obtains the string’s length via the strlen()<\/em> function. To get the position of the rightmost size<\/code> characters, I use the calculation string+len-size-1<\/code>. In this expression, string+len<\/code> calculates the end of the string, where the null character ('\\0'<\/code>) dwells. Subtract the value of size<\/code>, plus 1 for the null character, to find the starting location of the rightmost size<\/code> characters in string<\/code>. That location (a pointer) is returned.<\/p>\n
The pointer variation on the right()<\/em> function doesn’t require the strlen()<\/em> function. Instead, I loop through the string to find the null character:<\/p>\n
\r\nchar *right(char *string, int size)\r\n{\r\n    while(*string++)\r\n        ;\r\n\r\n    return(string-size-2);\r\n}<\/pre>\n
The while<\/em> loop processes the string for each non-null character. It stops when *string=='\\0'<\/code>, but because of the ++<\/code> postfix, the pointer references the memory location after<\/em> the '\\0'<\/code>.<\/p>\n
In the return<\/em> statement, the value of size<\/code> is subtracted from string<\/code>‘s memory location. Because string<\/code> points at two characters beyond its end (the null character and whatever character follows it), the value 2 is subtracted.<\/p>\n
WARNING:<\/strong> This variation is risky because string<\/code> references a memory location beyond what’s allocated. A segmentation fault or similar error could generate at runtime should the memory location exist outside the program’s control.<\/p>\n
Both functions yield the same output in my sample code:<\/p>\n
http:\/\/c-for-dummies.com\/images\/c.png -> c.png\r\nhttp:\/\/www.c-for-dummies.com\/images\/c.png -> c.png\r\n\/c-for-dummies.com\/images\/c.png -> c.png<\/code><\/pre>\n
Click here<\/a> to view the first, string solution.<\/p>\n
Click here<\/a> to view the second, pointer solution.<\/p>\n
If you came up with a different solution, wonderful! Ensure that you test your function to ensure that the rightmost n<\/em> characters of the string are returned. I ran my functions through the paces, and they worked fine — just like that old BASIC language RIGHT$ function from long ago.<\/p>\n","protected":false},"excerpt":{"rendered":"
For this month’s Exercise, I offer both a string function solution as well as a solution that uses pointers. As you can guess, I thought of the string method first, which is where most programmers would run to avoid the … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-2737","post","type-post","status-publish","format-standard","hentry","category-solution"],"_links":{"self":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/2737","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2737"}],"version-history":[{"count":5,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/2737\/revisions"}],"predecessor-version":[{"id":2766,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/2737\/revisions\/2766"}],"wp:attachment":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2737"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2737"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2737"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}