Where are
MINandMAXdefined in C, if at all?
They aren't.
What is the best way to implement these, as generically and type safe as possible (compiler extensions/builtins for mainstream compilers preferred).
As functions. I wouldn't use macros like #define MIN(X, Y) (((X) < (Y)) ? (X) : (Y)), especially if you plan to deploy your code. Either write your own, use something like standard fmax or fmin, or fix the macro using GCC's typeof (you get typesafety bonus too) in a GCC statement expression:
#define max(a,b) \
({ __typeof__ (a) _a = (a); \
__typeof__ (b) _b = (b); \
_a > _b ? _a : _b; })
Everyone says "oh I know about double evaluation, it's no problem" and a few months down the road, you'll be debugging the silliest problems for hours on end.
Note the use of __typeof__ instead of typeof:
Answer from David Titarenco on Stack OverflowIf you are writing a header file that must work when included in ISO C programs, write
__typeof__instead oftypeof.
Where are
MINandMAXdefined in C, if at all?
They aren't.
What is the best way to implement these, as generically and type safe as possible (compiler extensions/builtins for mainstream compilers preferred).
As functions. I wouldn't use macros like #define MIN(X, Y) (((X) < (Y)) ? (X) : (Y)), especially if you plan to deploy your code. Either write your own, use something like standard fmax or fmin, or fix the macro using GCC's typeof (you get typesafety bonus too) in a GCC statement expression:
#define max(a,b) \
({ __typeof__ (a) _a = (a); \
__typeof__ (b) _b = (b); \
_a > _b ? _a : _b; })
Everyone says "oh I know about double evaluation, it's no problem" and a few months down the road, you'll be debugging the silliest problems for hours on end.
Note the use of __typeof__ instead of typeof:
If you are writing a header file that must work when included in ISO C programs, write
__typeof__instead oftypeof.
It's also provided in the GNU libc (Linux) and FreeBSD versions of sys/param.h, and has the definition provided by dreamlax.
On Debian:
$ uname -sr
Linux 2.6.11
$ cat /etc/debian_version
5.0.2
$ egrep 'MIN\(|MAX\(' /usr/include/sys/param.h
#define MIN(a,b) (((a)<(b))?(a):(b))
#define MAX(a,b) (((a)>(b))?(a):(b))
$ head -n 2 /usr/include/sys/param.h | grep GNU
This file is part of the GNU C Library.
On FreeBSD:
$ uname -sr
FreeBSD 5.5-STABLE
$ egrep 'MIN\(|MAX\(' /usr/include/sys/param.h
#define MIN(a,b) (((a)<(b))?(a):(b))
#define MAX(a,b) (((a)>(b))?(a):(b))
The source repositories are here:
- GNU C Library
- FreeBSD
Videos
The C programming language is missing library functions min and max for integer types. I am not aware of any argument to not provide them, given virtually every programming language providing them.
Relevance
For floats and doubles, fmin and fmax exists, but not for integer types. Other programming language provide them including C++ by std::min and std::max. Several C libraries provide them too, e.g., Linux, SuperLU, Cairo. Stackoverflow has a question with more then 400 upvotes, indicating that this is a real issue.
Add to C language?
Is it worthwhile to write a paper suggesting the addition of min and max? Or is there a reason that their addition has not already happened?
Yes, minimum of the two numbers in the parentheses.
Note that the minimum is not always well-defined. For example, given the interval $(0,1)$, there is no smallest element in the interval, since we may find numbers in the interval arbitrarily close to zero. So the minimum (and maximum) are not always well defined. We may use infimums and supremums to fix this problem.
When learning about the min and max operations, I think it's important to know their limitations.