{"id":1048,"date":"2014-11-08T00:01:19","date_gmt":"2014-11-08T08:01:19","guid":{"rendered":"http:\/\/c-for-dummies.com\/blog\/?p=1048"},"modified":"2014-11-15T07:42:41","modified_gmt":"2014-11-15T15:42:41","slug":"functions-in-functions","status":"publish","type":"post","link":"https:\/\/c-for-dummies.com\/blog\/?p=1048","title":{"rendered":"Functions in Functions!"},"content":{"rendered":"

For an argument, functions in the C language can take literal values, equations, the result from another function, or any combination of these items. It’s a feature that’s both flexible and confusing.
\n
\nAs an example, consider these three printf()<\/em> functions:<\/p>\n

printf(\"The result is %d\\n\",27);<\/code><\/p>\n

printf(\"The result is %d\\n\",13+alpha);<\/code><\/p>\n

printf(\"The result is %d\\n\",blorf());<\/code><\/p>\n

The first statement uses a literal value. The second uses an equation, 13+alpha<\/code><\/code>, and the final uses the return value of the function blorf()<\/em>, which you can assume generates an integer.<\/p>\n

It’s also possible to put the same function inside itself, as the following code demonstrates:<\/p>\n

\r\n#include <stdio.h>\r\n\r\nint twice(int v);\r\n\r\nint main()\r\n{\r\n    int x;\r\n\r\n    x = twice(twice(2));\r\n    printf(\"The result is %d\\n\",x);\r\n\r\n    return(0);\r\n}\r\n\r\nint twice(int v)\r\n{\r\n    return(v*2);\r\n}<\/pre>\n
At Line 9, the twice()<\/em> function uses the result of the twice()<\/em> function to calculate its value.<\/p>\n
Don’t freak out: No quantum particles were entangled to perform this type of operation. As with the sample printf()<\/em> statements earlier, you simply need to work from inside the parentheses outward:<\/p>\n
x = twice(twice(2));<\/code><\/p>\n
The first operation is twice(2)<\/code>, which simply doubles the value 2. The result 4 is returned.<\/p>\n
The result 4 is again passed to the twice()<\/em> function, and the result 8 is returned.<\/p>\n
Here’s the output:<\/p>\n
The result is 8<\/code><\/pre>\n
You could even get really carried away and do something like this for Line 9:<\/p>\n
x = twice(twice(twice(twice(2))));<\/code><\/p>\n
That all still works, providing you properly match up the parentheses.<\/p>\n
What you need to be careful of, however, is when you use a function within<\/em> that same function. For example:<\/p>\n
\r\nint twice(int v)\r\n{\r\n    return(twice(v*2));\r\n}<\/pre>\n
In the return<\/em> statement, the function twice()<\/em> calls itself again. This is a perfectly legal maneuver in the C language. It’s called recursion<\/em>.<\/p>\n
re-kur-shn<\/em><\/p>\n
The problem with the above example is that it’s a recursion without exit, so the function twice()<\/em> would keep calling itself, doubling the value of v<\/code>, until a nasty condition called a stack overflow<\/em> occurs. That’s something you want to avoid.<\/p>\n
You can craft a function to be recursive. You’ll find many advantages to doing so, although be aware that it’s a tricky and advanced programming concept. I’ll gingerly explore the operation in next week’s Lesson<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"
A function can go inside a function, even when it’s the same function. Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"class_list":["post-1048","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\/1048","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=1048"}],"version-history":[{"count":6,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/1048\/revisions"}],"predecessor-version":[{"id":1096,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/1048\/revisions\/1096"}],"wp:attachment":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1048"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1048"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1048"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}