Re: [IDEA+RFC] Possible solution for min()/max() war

[David Lang <dlang@diginsite.com>]

Brad, the three arg min/max changes both values to the common type and
then compares them.

there isn't any need to have two different types becouse you then still
need to decide what the common type you are going to use for the
comparison is.

David Lang

 On Tue, 28 Aug 2001, Brad Chapman wrote:

> Date: Tue, 28 Aug 2001 12:33:17 -0700 (PDT)
> From: Brad Chapman <kakadu_croc@yahoo.com>
> To: linux-kernel@vger.kernel.org
> Subject: Re: [IDEA+RFC] Possible solution for min()/max() war
>
> Everyone,
>
> 	From reading this thread, I believe I have come up with several reasons,
> IMHO, why the old min()/max() macros were not usable:
>
> 	- They did not take into account non-typesafe comparisons
> 	- They were too generic
> 	- Some versions, IIRC, relied on typeof()
> 	- They did not take into account signed/unsigned conversions
>
> 	I have also discovered one problem with the new three-arg min()/max()
> macro: it forces both arguments to be the same, thus preventing signed/unsigned
> comparisons.
>
> 	Thus, I have a humble idea: add another type argument!
>
> 	Below is a coding example (just an example!):
>
> 	#define min(ta, a, tb, b)	((ta)(a) < (tb)(b) ? (a) : (b))
> 	#define max(ta, a, tb, b)	((ta)(a) > (tb)(b) ? (a) : (b))
>
> 	.....
> 	long int number[] = { 878593, 786831 };
> 	short int num[] = { 878, 786 };
>
> 	.....
> 	long_min = min(long int, num[0], long int, number[0]);
> 	short_min = min(short int, num[0], short int, number[0]);
>
> 	long_max = max(long int, num[1], long int, number[1]);
> 	short_max = max(short int, num[1], short int, number[1]);
>
> 	Thus, people can now cast different number types up or down, depending
> on what they need, and properly compare their sizes. The new argument also makes
> comparisons between signed/unsigned more flexible, because now you can cast
> in both directions - get a signed minimum and an unsigned minimum.
>
> 	This is an RFC. Flames, anyone? Honestly, this was one of those
> "lightbulb" ideas. If people object, I don't mind......
>
> Brad
>
> P.S: /me also wonders if I will need firehoses in my e-mail client ;)
>
> > On 28 Aug 2001, Andreas Schwab wrote:
> >
> > > Roman Zippel <zippel@linux-m68k.org> writes:
> > >
> > > |> Hi,
> > > |>
> > > |> Linus Torvalds wrote:
> > > [...]
> > > |> > You just fixed the "re-use arguments" bug - which is a bug, but doesn't
> > > |> > address the fact that most of the min/max bugs are due to the programmer
> > > |> > _indending_ a unsigned compare because he didn't even think about the
> > > |> > type.
> >
> >
> > #if 0
> > If the comparison was made unsigned, cast to the largest natural
> > value on the target, while keeping the types and sizes of the
> > input variables the same, this macro does about what 99.9999999 percent
> > of what everybody wants:
> > #endif
> >
> > #include <stdio.h>
> >
> > #define min(a,b) ((size_t)(a) < (size_t)(b) ? (a) : (b))
> >
> > int main()
> > {
> >     printf("%d\n", min(1,2));
> >     printf("%d\n", min(-1,2));
> >     printf("%d\n", min(0xffffffff,3));
> >     printf("%d\n", min(0x8000,4));
> >     printf("%d\n", min(0x7fff,5));
> >     printf("%d\n", min(0x80000000,6));
> >     printf("%d\n", min(0x7fffffff,7));
> >
> >     printf("%ld\n", min(1L,2L));
> >     printf("%ld\n", min(-1L,2L));
> >     printf("%ld\n", min(0xffffffff,3L));
> >     printf("%ld\n", min(0x8000,4L));
> >     printf("%ld\n", min(0x7fff,5L));
> >     printf("%ld\n", min(0x80000000,6L));
> >     printf("%ld\n", min(0x7fffffff,7L));
> >
> >     printf("%lu\n", min(1L,2LU));
> >     printf("%lu\n", min(-1L,2LU));
> >     printf("%lu\n", min(0xffffffff,3LU));
> >     printf("%lu\n", min(0x8000,4LU));
> >     printf("%lu\n", min(0x7fff,5LU));
> >     printf("%lu\n", min(0x80000000,6LU));
> >     printf("%lu\n", min(0x7fffffff,7LU));
> >
> >     printf("%d\n", min(-1, -2));
> >     printf("%d\n", min(-1, 0));
> >     printf("%p\n", min((void *)0x80000000, (void *)0x7fffffff));
> >     return 0;
> > }
> >
> >
> >
> > Cheers,
> > Dick Johnson
> >
> > Penguin : Linux version 2.4.1 on an i686 machine (799.53 BogoMips).
> >
> >     I was going to compile a list of innovations that could be
> >     attributed to Microsoft. Once I realized that Ctrl-Alt-Del
> >     was handled in the BIOS, I found that there aren't any.
> >
> >
> > -
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>
>
> =====
> Brad Chapman
>
> Permanent e-mail: kakadu_croc@yahoo.com
> Current e-mail: kakadu@adelphia.net
> Alternate e-mail: kakadu@netscape.net
>
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