Don’t keep track of information you don’t need<\/I>.\nI remember being asked to look at a customer’s program,\nand one thing that struck me was that the program had\na bazillion different flag variables that it spent a lot of time\nsetting and clearing. Here’s an oversimplified example:\n<\/P>\n\nvoid CConfiguration::ShowDialog(HWND hwnd)\n{\n m_fShowingDialog = true;\n DoModal(hwnd);\n m_fShowingDialog = false;\n m_fDialogHasBeenShown = true;\n}\n<\/PRE>\n\nA naïve reading of the code would lead one to believe that\nthe main purpose of the program was to set and clear flags!\nUpon closer inspection, I found that most of the flag\nvariables were write-only.\nAlthough the code went to great pains to update the flags\nas it ran,\nthere was no code that actually cared whether the flag was set or not.\n<\/P>\n
\nI asked the customer liaison about this, thinking that maybe\nI missed something.\nMaybe the variables were being used in a subtle way that I failed\nto appreciate.\nMaybe they were used during debugging.\n<\/P>\n
\nThe customer liaison got back to me.\n“When I asked them about it, they just said, ‘Ah, yes.’\nApparently that code was written by one of their guys named Bob.\nI guess he likes to set and clear flags a lot.”\n<\/P>\n
\nBut is there any code that actually checks the values of those flags?<\/I>\n<\/P>\n
\n“Probably not.\nHe just set and cleared those flags because he figured maybe someday\nhe might need them.”\n<\/P>\n
\nIndeed, once in a while, he actually tested one of the dozens of flags\nhe spent most of his time setting and resetting.\nBut the vast majority of the flags were write-only.\n(And since most of the flags went unused,\nI suspect that many of them weren’t even accurate.)\n<\/P>\n
\nObviously, this is an extreme case of write-only variables,\nbut it illustrates the point.\nNext time, we’ll look at one of the consequences of the principle\nof not keeping track of information you don’t need.\n<\/P><\/p>\n","protected":false},"excerpt":{"rendered":"
This is sort of an extreme corollary to Don’t save anything you can recalculate. Sure, it sounds like such an obvious principle, but many people fail to understand its consequences. Let’s look at the principle again. Don’t keep track of information you don’t need. I remember being asked to look at a customer’s program, and […]<\/p>\n","protected":false},"author":1069,"featured_media":111744,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[25],"class_list":["post-19133","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":"
This is sort of an extreme corollary to Don’t save anything you can recalculate. Sure, it sounds like such an obvious principle, but many people fail to understand its consequences. Let’s look at the principle again. Don’t keep track of information you don’t need. I remember being asked to look at a customer’s program, and […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/19133","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/users\/1069"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/comments?post=19133"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/19133\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media\/111744"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media?parent=19133"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=19133"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=19133"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}