{"id":4285,"date":"2020-08-08T00:01:39","date_gmt":"2020-08-08T07:01:39","guid":{"rendered":"https:\/\/c-for-dummies.com\/blog\/?p=4285"},"modified":"2020-08-08T07:57:30","modified_gmt":"2020-08-08T14:57:30","slug":"the-switch-condition","status":"publish","type":"post","link":"https:\/\/c-for-dummies.com\/blog\/?p=4285","title":{"rendered":"The switch<\/em> Condition"},"content":{"rendered":"

\"switch
\nA switch-case<\/em> structure performs a complex decision in your code, similar to a cascade of if else-if else<\/em> statements. The structure works like a comparison as a whole, acting upon single values or variables. But its construction need not lack expressions.
\n
\nIn my books, I describe the switch<\/em> statement like this:<\/p>\n

Unlike an if<\/em> statement, switch<\/em> eats only a single value.<\/p><\/blockquote>\n

And I describe case<\/em> like this:<\/p>\n

A case<\/em> statement shows a single value . . . followed by a colon.<\/p><\/blockquote>\n

It’s true that switch<\/em> and case<\/em> operate on single values, either a variable, constant, or literal value. But they can also work with expressions. The key is that the expression must result in a single value, as this code demonstrates:<\/p>\n

2020_08_08-Lesson-a<\/a><\/h3>\n
\r\n#include <stdio.h>\r\n\r\nint main()\r\n{\r\n    switch( 4-2 )\r\n    {\r\n        case 4:\r\n            puts(\"The answer is 4\");\r\n            break;\r\n        case 3:\r\n            puts(\"The answer is 3\");\r\n            break;\r\n        case 2:\r\n            puts(\"The answer is 2\");\r\n            break;\r\n        case 1:\r\n            puts(\"The answer is 1\");\r\n            break;\r\n        case 0:\r\n            puts(\"The answer is 0\");\r\n            break;\r\n        default:\r\n            puts(\"I don't know!\");\r\n    }\r\n\r\n    return(0);\r\n}<\/pre>\n
At Line 5, the switch<\/em> keyword’s parentheses feature an expression, ( 4-3 )<\/code>. It’s not a comparison; the comparison happens between the result of the switch<\/em> expression and what follows the case<\/em> keywords in the structure. The results of the expression is 2 and the case 2:<\/code> statement’s (starting at Line 13) are executed.<\/p>\n
As with switch<\/em>, the case<\/em> keywords can also sport an expression, providing it returns a single value:<\/p>\n
2020_08_08-Lesson-b<\/a><\/h3>\n
\r\n#include <stdio.h>\r\n\r\nint main()\r\n{\r\n    switch( 4-2 )\r\n    {\r\n        case (4-0):\r\n            puts(\"The answer is 4\");\r\n            break;\r\n        case (4-1):\r\n            puts(\"The answer is 3\");\r\n            break;\r\n        case (4-2):\r\n            puts(\"The answer is 2\");\r\n            break;\r\n        case (4-3):\r\n            puts(\"The answer is 1\");\r\n            break;\r\n        case (4-4):\r\n            puts(\"The answer is 0\");\r\n            break;\r\n        default:\r\n            puts(\"I don't know!\");\r\n    }\r\n\r\n    return(0);\r\n}<\/pre>\n
Of course, this example is pedantic; obviously 4-2<\/code> matches 4-2<\/code>. Still, it’s the result that’s compared, not the literal expression.<\/p>\n
What happens when you use a comparison in a switch<\/em> statement? Oo! Let’s find out:<\/p>\n
2020_08_08-Lesson-c<\/a><\/h3>\n
\r\n#include <stdio.h>\r\n\r\nint main()\r\n{\r\n    int a,b;\r\n\r\n    a = 10;\r\n    b = -10;\r\n\r\n    switch( a > b  )\r\n    {\r\n        case 1:\r\n            printf(\"%d is greater than %d\\n\",a,b);\r\n            break;\r\n        case 0:\r\n            printf(\"%d is not greater than %d\\n\",a,b);\r\n            break;\r\n        default:\r\n            puts(\"I'm not sure what's going on\");\r\n    }\r\n\r\n    return(0);\r\n}<\/pre>\n
This code compiles with a warning. The switch<\/em> statement’s expression at Line 10 is a “boolean.” Still, this warning doesn’t stop the program from being built. Here’s the output:<\/p>\n
10 is greater than -10<\/code><\/p>\n
You can suppress the warning by casting the switch<\/em> statement like this:<\/p>\n
switch( (int)(a > b)  )<\/code><\/p>\n
Still it’s easier to use an if<\/em> statement instead. After all, it’s the right tool for the job.<\/p>\n","protected":false},"excerpt":{"rendered":"
The switch<\/em> statement need not contain a single value or variable. 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-4285","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\/4285","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=4285"}],"version-history":[{"count":7,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/4285\/revisions"}],"predecessor-version":[{"id":4303,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/4285\/revisions\/4303"}],"wp:attachment":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4285"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4285"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4285"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}