The C Preprocessor and pound Defines - Revision history

Russ hensel at 18:43, 3 October 2009

2009-10-03T18:43:24Z

Russ hensel at 18:43, 3 October 2009

2009-10-03T18:43:01Z

Russ hensel: moved The C Preprocessor and to The C Preprocessor and pound Defines: # define is a problem

2009-10-03T18:37:30Z

moved The C Preprocessor and to The C Preprocessor and pound Defines: # define is a problem

Russ hensel: /* More Reading */

2009-10-03T18:25:40Z

Russ hensel: /* Calculations */

2009-05-20T02:24:35Z

Calculations

Russ hensel: /* More Reading */

2009-05-20T02:15:43Z

Russ hensel: /* More Reading */

2009-05-20T02:14:08Z

Russ hensel at 01:16, 20 May 2009

2009-05-20T01:16:33Z

Russ hensel: New page: Early draft, may not be useful to read Programming in C almost always involves using and learning about the pre processor. The preprocessore is a program that takes your program as inp...

2009-05-19T20:37:20Z

New page: Early draft, may not be useful to read Programming in C almost always involves using and learning about the pre processor. The preprocessore is a program that takes your program as inp...

New page

Early draft, may not be useful to read

Programming in C almost always involves using and learning about the pre processor. The preprocessore is a program that takes your program as input and outputs the program somewhat transformed.

The #define may be the most important part of the preprocessor. A #define simply defines one symbol as a shorthand for another symbol, all the data is text or string. For example

#define BIG 255

Simply means that every place that the string BIG occurs in the program it means the string 255. The preprocessor actually makes this substution. There is no notion that 255 is a number, it is just a string, later the compiler will see the 255 and it, not the preprocessor will view it as a number.

Calculations

#define BIGGER 255 + 5

just looks like a calculation, actually it means that BIGGER is just the same as the text 250 + 5, only later in the compiler will 255 + 5 be interperted as a number where:

x = a + BIGGER;

becomes

x = a + 255 + 5;

Other places in this wiki where the preprocessor is discussed:

boostc h files

[[Index of sample code pages]]

External links to preprocessor information:

@@ Line 1: / Line 1: @@
 Early draft, may not be useful to read
-Or:  The C Preprocssor and #Defines ( #define seems to be illegal in the title of a page )
+Or:  The C Preprocssor and #Defines ( #Define seems to be illegal in the title of a page )
 == Overview ==

@@ Line 1: / Line 1: @@
 Early draft, may not be useful to read
+Or:  The C Preprocssor and #Defines ( #define seems to be illegal in the title of a page )
 == Overview ==

← Older revision		Revision as of 18:25, 3 October 2009
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	* [http://publications.gbdirect.co.uk/c_book/chapter7/directives.html 7.3. Directives]		* [http://publications.gbdirect.co.uk/c_book/chapter7/directives.html 7.3. Directives]
		+
		+	* [http://www.gamedev.net/reference/articles/article1798.asp Organizing Code Files in C and C++] Not just the preprocessor but more general information on the structure of projects.


	[[Category:PIC]][[Category:BoostC]]		[[Category:PIC]][[Category:BoostC]]

← Older revision		Revision as of 02:24, 20 May 2009
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	== Calculations ==		== Calculations ==

		+	The ability to do calculations with the preprocessor is a bit odd, as shown above most of the #define work simply does text substution, with the effect of calculation comming in the compiler optimization. There is an odd way of doing calculations, the #if directive will evalue what follows it interperting the symbols as long integers, and treating 0 as false and anything else as true. You can do the calculation, and even compare the result with ==, but there does not seem to be any direct way of saving the result. Here is an example:
		+
		+
		+	Look at the links below for more information about #if and related directives.
		+
		+
		+	== Messages in the Output ==
		+
		+	#warning yyyy
		+
		+	sends warning yyyy to the output and continues the compilation process ( actually in the preprocessor )
		+
		+	#error xxxxxx
		+
		+	sends error xxxxxx to the output and ends compilation process

	== How C Compiles ==		== How C Compiles ==

← Older revision		Revision as of 02:15, 20 May 2009
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	* [http://publications.gbdirect.co.uk/c_book/chapter7/directives.html 7.3. Directives]		* [http://publications.gbdirect.co.uk/c_book/chapter7/directives.html 7.3. Directives]
		+
		+
		+	[[Category:PIC]][[Category:BoostC]]

← Older revision	Revision as of 18:37, 3 October 2009
(No difference)

← Older revision		Revision as of 02:14, 20 May 2009
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		+	External links to preprocessor information:


		+	* [http://gcc.gnu.org/onlinedocs/gcc-3.0.1/cpp_3.html#SEC33 3. Macros]

		+	* [http://gcc.gnu.org/onlinedocs/cpp/ The C Preprocessor]

−	~~External links to preprocessor information~~:	+	* [http://publications.gbdirect.co.uk/c_book/chapter7/directives.html 7.3. Directives]

@@ Line 1: / Line 1: @@
 Early draft, may not be useful to read
+== Overview ==
 Programming in C almost always involves using and learning about the pre processor.  The preprocessore is a program that takes your program as input and outputs the program somewhat transformed.
@@ Line 23: / Line 23: @@
         x = a + 255 + 5;
 Other places in this wiki where the preprocessor is discussed: