{"id":4246,"date":"2020-07-18T00:01:02","date_gmt":"2020-07-18T07:01:02","guid":{"rendered":"https:\/\/c-for-dummies.com\/blog\/?p=4246"},"modified":"2022-11-20T09:48:02","modified_gmt":"2022-11-20T17:48:02","slug":"getting-to-the-square-root-of-the-problem","status":"publish","type":"post","link":"https:\/\/c-for-dummies.com\/blog\/?p=4246","title":{"rendered":"Getting to the Square Root of the Problem"},"content":{"rendered":"

The first part of my writing career began by updating a computer book bestseller, The BASIC Handbook<\/em>. This tome served as a lexicon for the various BASIC programming language dialects, allowing users from one version of BASIC to translate and use code from another version.
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Figure 1. The BASIC Handbook<\/em>, Compusoft Publishing, 1986.<\/p><\/div><\/p>\n

One of the more interesting parts of the book included BASIC code in the form of a generic algorithm. You could use the algorithm in case your version of BASIC lacked a command available for other versions.<\/p>\n

For example, if your version of BASIC lacked the absolute value command, ABS<\/code>, you could write your own. From the book:<\/p>\n

\r\n29999 END\r\n30000 REM * 'ABS' SUBROUTINE *\r\n30010 REM * INPUT IS X, OUTPUT IS Y *\r\n30020 Y = X\r\n30030 IF X>=0 THEN 30060\r\n30040 Y = -X\r\n30050 RETURN<\/pre>\n
Looking back on that code in the book, it’s amazing how sloppy BASIC can be. Further, I found a typo: Line 30030 incorrectly lists Line 30060 as the RETURN<\/code> command. It should be 30050. Ugh.<\/p>\n
Generally speaking, C programmers are familiar with this book’s approach for missing functions. C lacks many of the higher-level functions of other languages. So programmers write their own. In fact, sites like https:\/\/stackoverflow.com\/<\/a> are rife with examples of “missing” C language functions.<\/p>\n
Still, it’s intriguing for me to read algorithms that handle functions we take for granted. One of these mentioned in the book is the square root command.<\/p>\n
From The BASIC Handbook<\/em>, if your version of BASIC lacked the SQR<\/code> (square root) command you could substitute the following code:<\/p>\n
\r\n29999 END\r\n30000 REM * SQUARE ROOT SUBROUTINE *\r\n30010 REM * INPUT X, OUTPUT Y *\r\n30020 REM * ALSO USES W AND Z *\r\n30030 IF X = 0 THEN 30160\r\n30040 IF X>0 THEN 30070\r\n30050 PRINT \"ERROR - NEGATIVE ROOT\"\r\n30060 STOP\r\n30070 Y = X\/4\r\n30080 Z = 0\r\n30090 W = (X\/Y-Y)\/2\r\n30100 IF W = 0 THEN 30160\r\n30110 IF W = Z THEN 30160\r\n30120 Y = Y + W\r\n30130 Z = W\r\n30140 GOTO 30090\r\n30150 Y = 0\r\n30160 RETURN<\/pre>\n
Again, this code has a boner in it: Line 30150 will never be interpreted. I believe the implied GOTO<\/code> at Line 30030 should branch to Line 30150, though it instead goes to the RETURN<\/code> command at Line 30160. Whatever. Because most versions of BASIC implemented the square root (SQR<\/code>)  command, no one probably ever used this code. I’m not even certain the testers ran it. I don’t remember.<\/p>\n
Anyway, I thought it would be fun to translate this code into C just to see whether it works. After all, code is code; a lot of what’s written above translates directly into C. With a few modifications, I’d roll my own sqrt()<\/em> function. Wouldn’t that be grand?<\/p>\n
As it turns out, the thing didn’t work. I won’t even bother posting my code because the algorithm, at least as I translated it into C, died in an endless loop. The BASIC code above is most likely flawed. Pity.<\/p>\n
Not one to give up, I decided to craft my own square root function. I’d start from scratch, determining how a square root is calculated in the first place — well, other than using a calculator, which is probably what I was taught in school.<\/p>\n
I explore how to calculate a square root in next week’s Lesson<\/a>, where I introduce my square root substitute function.<\/p>\n","protected":false},"excerpt":{"rendered":"
What if the sqrt()<\/em> function didn’t exist! What would you do? 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":[2],"tags":[],"class_list":["post-4246","post","type-post","status-publish","format-standard","hentry","category-main"],"_links":{"self":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/4246","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=4246"}],"version-history":[{"count":5,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/4246\/revisions"}],"predecessor-version":[{"id":5656,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/4246\/revisions\/5656"}],"wp:attachment":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4246"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4246"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4246"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}