<\/p>\n
For the C programmers, here’s a little puzzle that I first produced while banging my head against the C syntax at uni. Actually its more like a magic trick.<\/p>\n
Start by having a look at the following “code”. It starts out well – and it finishes well. But it gets a bit distracted in the middle.<\/p>\n
#include <stdio.h>\r\n\r\nint main()\r\n{\r\n float eight = 8.0;\r\n float *pEight = &eight;\r\n float oneEighth = 1.0\/*pEight;\r\n\r\n oneEighth += oneEighth;\r\n \/\/ If you are using a C++ compiler, this line will be ignored as a comment.\r\n \/\/ That's a shame because it is the previous line which is buggy!\r\n\r\n #if(this) was Python, this buggy line would be ignored: oneEighth += oneEighth;\r\n\r\n <!-- If this was HTML, however, it would be this buggy line that was ignored:\r\n oneEighth += oneEighth; -->\r\n\r\n \/\/ As you can see, C has a remarkably complicated syntax for a relatively small language.\r\n \/\/ It is too hard to predict, and is full of nasty tricks. I don't like its syntax much. \r\n \/\/ I wish other languages didn't copy it.\r\n \/\/ In fact, frankly, I think its syntax is a load of #%$@*\/;\r\n\r\n printf(\"The final value of oneEighth = %f\\n\", oneEighth);\r\n return 0;\r\n}\r\n<\/code><\/pre>\nSo, what will happen when you compile this code? Answer below, so have a stab before reading on.<\/p>\n
<\/more><\/p>\nThe answer is surprising – here’s bit where people get dazzled by the magic when I demonstrate it in front of them.<\/p>\n
You don’t get any error message at all! This is valid C code! It compiles and it runs. No honestly. I even checked that WordPress didn’t chew it up. You can try it for yourself, later.<\/p>\n
But that’s not the weird part! The weird part is what happens when you run it! This is what it prints to stdout:<\/p>\n
The final value of oneEighth = 1.000000\r\n<\/code><\/pre>\nWeird! So how could it have successfully doubled the value of oneEighth<\/code> three times, despite the various commenting standards?<\/p>\nHave you figured it out yet? <\/p>\n
I stumbled over this trick before the syntax-colouring was popular; I had a genuine bug in my code caused by the same trick. However, these days, pasting this text into a syntax-colouring editor makes the trick so obvious, I won’t even bother to reveal the solution here.<\/p>\n","protected":false},"excerpt":{"rendered":"
A magic trick for C programmers to try,<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_s2mail":"","footnotes":""},"categories":[28,33,34],"tags":[],"class_list":["post-100","post","type-post","status-publish","format-standard","hentry","category-doubleplus-geek","category-puzzle-solving","category-software-development"],"_links":{"self":[{"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/posts\/100","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/comments?post=100"}],"version-history":[{"count":0,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/posts\/100\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/media?parent=100"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/categories?post=100"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.somethinkodd.com\/oddthinking\/wp-json\/wp\/v2\/tags?post=100"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}