Range-based for loop - Revision history

Vegard: /* Usage */ add output

2020-04-28T08:43:54Z

Usage: add output

@@ Line 18: / Line 18: @@
 === Usage ===
 <source lang="C">
 for RANGE(i, -1, 5) {
@@ Line 23: / Line 29: @@
+}
 </source>
 [[Category:C]]

Vegard: add ranges

2020-04-28T08:21:49Z

add ranges

← Older revision		Revision as of 08:21, 28 April 2020
Line 4:		Line 4:

	<source lang="C">		<source lang="C">
			// low .. (high - 1)
	#define RANGE(var, low, high) \		#define RANGE(var, low, high) \
	(typeof(0 ? (low) : (high)) var = (low), _end = (high); var < _end; ++var)		(typeof(0 ? (low) : (high)) var = (low), _end = (high); var < _end; ++var)

	// https://stackoverflow.com/a/5458283		// https://stackoverflow.com/a/5458283
			// (high - 1) .. low
	#define REVERSE_RANGE(var, high, low) \		#define REVERSE_RANGE(var, high, low) \
	(typeof(0 ? (low) : (high)) var = (high), _end = (low); var-- > _end; )		(typeof(0 ? (low) : (high)) var = (high), _end = (low); var-- > _end; )

Vegard: fix bug

2020-03-10T09:02:56Z

fix bug

← Older revision		Revision as of 09:02, 10 March 2020
Line 5:		Line 5:
	<source lang="C">		<source lang="C">
	#define RANGE(var, low, high) \		#define RANGE(var, low, high) \
	(typeof(0 ? (low) : (high)) var = (low), _end = (high); var < _end; ++var)		(typeof(0 ? (low) : (high)) var = (low), _end = (high); var < _end; ++var)

	// https://stackoverflow.com/a/5458283		// https://stackoverflow.com/a/5458283
	#define REVERSE_RANGE(var, high, low) \		#define REVERSE_RANGE(var, high, low) \
	(typeof(0 ? (low) : (high)) var = (high), _end = (low); var-- > _end; )		(typeof(0 ? (low) : (high)) var = (high), _end = (low); var-- > _end; )
	</source>		</source>

	This automatically deduces the type of the index variable, so that e.g. <tt>RANGE(i, -1, 1)</tt> will use <tt>int</tt>, while <tt>RANGE(i, 0U, 1U)</tt> will use <tt>unsigned long</tt>. Note that <tt>typeof</tt> is a GNU/gcc extension, so this will not work on e.g. MSVC.		This automatically deduces the type of the index variable, so that e.g. <tt>RANGE(i, -1, 1)</tt> will use <tt>int</tt>, while <tt>RANGE(i, 0UL, 1UL)</tt> will use <tt>unsigned long</tt>. Note that <tt>typeof</tt> is a GNU/gcc extension, so this will not work on e.g. MSVC.

	=== Usage ===		=== Usage ===
Line 18:		Line 18:
	<source lang="C">		<source lang="C">
	for RANGE(i, -1, 5) {		for RANGE(i, -1, 5) {
	printf("%d\n", i);		printf("%d\n", i);
	}		}
	</source>		</source>

Vegard: add category

2020-03-01T11:53:47Z

add category

← Older revision		Revision as of 11:53, 1 March 2020
Line 24:		Line 24:
	[[Category:C]]		[[Category:C]]
	[[Category:Programming]]		[[Category:Programming]]
			[[Category:C preprocessor snippets]]

Vegard: clarify

2020-02-29T19:52:04Z

clarify

← Older revision		Revision as of 19:52, 29 February 2020
Line 1:		Line 1:
	One of my pet peeves is the regular counting <tt>for</tt> loop in C where you have to repeat the variable name 3 times. This is error-prone in the case of nested loops, since the compiler has no way to know that you meant to increment <tt>j</tt> and not <tt>i</tt>. To prevent this kind of error, you can use a few helper macros that iterate over a range (forwards or backwards).		One of my pet peeves is the regular counting <tt>for</tt> loop in C where you have to repeat the variable name 3 times. This is error-prone in the case of nested loops, since the compiler has no way to know that you meant to increment <tt>j</tt> and not <tt>i</tt>. To prevent this kind of error, you can use a few helper macros that iterate over a range (forwards or backwards).

	Definitions:		=== Definitions ===

	<source lang="C">		<source lang="C">
Line 12:		Line 12:
	</source>		</source>

	Note that <tt>typeof</tt> is a GNU/gcc extension, so this will not work on e.g. MSVC.		This automatically deduces the type of the index variable, so that e.g. <tt>RANGE(i, -1, 1)</tt> will use <tt>int</tt>, while <tt>RANGE(i, 0U, 1U)</tt> will use <tt>unsigned long</tt>. Note that <tt>typeof</tt> is a GNU/gcc extension, so this will not work on e.g. MSVC.

	Usage:		=== Usage ===

	<source lang="C">		<source lang="C">

Vegard: new page

2020-02-29T17:35:51Z

new page

New page

One of my pet peeves is the regular counting <tt>for</tt> loop in C where you have to repeat the variable name 3 times. This is error-prone in the case of nested loops, since the compiler has no way to know that you meant to increment <tt>j</tt> and not <tt>i</tt>. To prevent this kind of error, you can use a few helper macros that iterate over a range (forwards or backwards).

Definitions:

<source lang="C">
#define RANGE(var, low, high) \
(typeof(0 ? (low) : (high)) var = (low), _end = (high); var < _end; ++var)

// https://stackoverflow.com/a/5458283
#define REVERSE_RANGE(var, high, low) \
(typeof(0 ? (low) : (high)) var = (high), _end = (low); var-- > _end; )
</source>

Note that <tt>typeof</tt> is a GNU/gcc extension, so this will not work on e.g. MSVC.

Usage:

<source lang="C">
for RANGE(i, -1, 5) {
printf("%d\n", i);
}
</source>

[[Category:C]]
[[Category:Programming]]