Some C coders really go nuts with macros. I’m not a big fan of those people.
\n
\nThe C language is obscure enough. When you add to that obscurity the use of macros, it makes a difficult language even more incomprehensible. Yet, some coders revel in that obfuscation.<\/p>\n
A few Lessons back<\/a>, someone asked me to describe how a loop works. I committed the terrible sin of actually explaining how a for<\/em> loop did its job. They just wanted to know, “Okay, so I need to repeat a chunk of code ten times.” That’s the kind of statement you get from a student who is required to take a programming course but doesn’t give a damn about learning anything.<\/p>\n Anyway, the C language lacks a direct looping keyword, but you can define one as a macro, which I did in this code example:<\/p>\n The The end result of the macro is seen in the main()<\/em> function: The repeat()<\/em> “function” processes a series of statements a given number of times. This kind of trick wouldn’t work with a true function; only a macro can set up such a statement within your code.<\/p>\n Another way to define the macro would be as follows:<\/p>\n Above, the repeat<\/em> macro is expanded into two statements. The first declares the int<\/em> variable My advice is to use Indeed, macros can get complicated when you stir variables into the mix. Continue reading \r\n#include <stdio.h>\r\n\r\n#define repeat( c ) for(int c1=0;c1<c;c1++)\r\n\r\nint main()\r\n{\r\n repeat(10)\r\n {\r\n puts(\"Hello!\");\r\n }\r\n\r\n return(0);\r\n}<\/pre>\n#define<\/code> preprocessor directive at Line 3 sets the repeat()<\/em> macro equal to a standard for<\/em> loop. Variable c<\/code> from the repeat<\/em> macro is placed into the for<\/em> loop at the proper locations to make a simple loop. Another variable, integer c1<\/code>, is created inside the for<\/em> statement with int c1=0<\/code>. That’s perfectly legal, providing that the variable isn’t declared elsewhere in the code.<\/p>\n#define repeat( c ) int c1 ; for(c1=0;c1<c;c1++)<\/code><\/pre>\nc1<\/code>. The second is the for<\/em> loop that uses variable c1<\/code> as well as variable c<\/code>. The program output is the same. My point is to demonstrate that a #define<\/code> macro can include more than a single statement. And that’s where things can get even more confusing.<\/p>\n#define<\/code> to create constants, which is common and expected. When you use #define<\/code> to shorten tangled code, that might be another good use, but my advice is to pull back on creating new function-like macros and otherwise obfuscating the text. While such antics may impress hard core C programmers, the end result is difficult to document and debug.<\/p>\n","protected":false},"excerpt":{"rendered":"