Min and max of a POD

What is the best way to get the minimum value
and the maximum value an integral POD can hold
without using any external definitions like INT_MIN, INT_MAX etc.?
The type (short, int, long, etc.) plus signed/unsigned is known.

re: Min and max of a POD

On Jul 2, 5:24*pm, "Adem24" <ade...@adem24adem24.org.invalidwrote:Why do you not want to use external definitions?
An alternative to those constants of course are from limits
i.e. numeric_limits<int>::max()

Joe Cook

re: Min and max of a POD

On Jul 2, 5:24*pm, "Adem24" <ade...@adem24adem24.org.invalidwrote:Would you be willing to make an assumption such as a two's complement
representation? Without some assumption like that, I see no way to
query the min/max without external definitions. With such an
assumption, the signed-ness can be queried without external
definitions as well.

-Howard

re: Min and max of a POD

joseph cook wrote:Just for the record, numeric_limits<int>::max() won't work under Visual
C++ because it defines two macros called "min" and "max", so the
preprocessor will try to expand the macro and the compiler will fail. It
really sucks.

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re: Min and max of a POD

"Howard Hinnant" wrote:How would a solution for a two's complement representation look like?

re: Min and max of a POD

On 3 Jul, 00:28, Fernando Gómez <fernando.a.gome...@gmail.comwrote:Only if you include a non-standard header that defines those macros.

DP

re: Min and max of a POD

On 2 Jul, 23:24, "Adem24" <ade...@adem24adem24.org.invalidwrote:For the unsigned types, a conversion from -1 should yield the maximum
value.

unsigned u = -1;

DP

re: Min and max of a POD

Fernando Gómez wrote:
Just for the record, define NOMINMAX before including the Windows
headers, as described in MS KB article 143208.

re: Min and max of a POD

On Jul 3, 12:28 am, Fernando Gómez <fernando.a.gome...@gmail.com>
wrote:Funny, I don't have that problem when I compile with VC++. Of
course, like most compilers, by default, it doesn't compile C++,
but only something rather similar, but if you give it the
necessary options, there's no problem. (As a minimum, I think
you need -vmg -GR -EHs -Zc:forScope,wchar_t -DNOMINMAX
-D_CRT_SECURE_NO_DEPRECATE. Some of these may not be necessary
with more recent versions of the compiler, however, and there
may be others which I've missed---since I don't use this
compiler professionally, I'm not fully up to date with it.)

--
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Conseils en informatique orientée objet/
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re: Min and max of a POD

On Jul 3, 12:23 am, Howard Hinnant <howard.hinn...@gmail.comwrote:For the unsigned, the representation of negative numbers is
irrelevant: the minimum is always 0, and the maximum
"~static_cast< Type >( 0 )" (or "static_cast< Type >( 0 ) - 1",
whichever you prefer).

For most systems, the maximum of a signed value can be obtained
by taking the maximum of the corresponding unsigned (as above),
then shifting it right 1 (still as unsigned). The minimum is a
bit tricky, but you should be able to do it by testing the 2
lower bits of -1, to add the special handling for 1's complement
and signed magnitude: I think the following should work:

- maximum - (static_cast< Type >( -1 ) & 3) == 3)

The only problem is on machines where the maximum value of an
unsigned is equal to the maximum value of the corresponding
signed. (The only two possibilities known to me are that the
unsigned uses the sign bit as part of its value, meaning that
shifting its max one to the right gives the max of a signed, or
that it ignores the sign bit, so that the max of the signed is
equal to the max of the unsigned. Regretfully, I don't know of
any way to determine which one holds, other than by using
external information. On the other hand, the only processor I
know where the unsigned simply ignore the sign bit is the Unisys
MCP, which isn't really a consideration for most people.)

In practice, of course, I use the constants defined in <climits>
if I need an integral constant expression, and the class
template numeric_limits (from <limits>) if I need the value for
a template argument. (And I wait until the next release of the
standard if I need both:-).)

--
James Kanze (GABI Software) email:james.kanze@gmail.com
Conseils en informatique orientée objet/
Beratung in objektorientierter Datenverarbeitung
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re: Min and max of a POD

Adem24 wrote:Templates might work.

template <typename T, T V, T W, T X, T Y, bool Z=true>
struct max_val
{
static const T newv = V << 1;
static const T neww = W + newv;

static const T val = max_val<T, newv, neww, V, W, (newv V)>::val;

};

template <typename T, T V, T W, T X, T Y>
struct max_val<T, V, W, X, Y, false>
{
static const T val = Y;
};

template <typename T>
struct maxof
{
static const T val = max_val<T,1,1,0,0,true>::val;
};


#include <iostream>

int main()
{
std::cout << "int " << maxof<int>::val << "\n";
std::cout << "unsigned int " << maxof<unsigned int>::val << "\n";
std::cout << "short " << maxof<short>::val << "\n";
std::cout << "char " << int(maxof<char>::val) << "\n";

}

re: Min and max of a POD

"Gianni Mariani" <gi4nospam@mariani.wswrote:
This code seems to be too complicated for the Microsoft C++ compiler: :-)

--------------------Configuration: test - Win32 Debug--------------------
Compiling...
test.cpp
C:\PRJ\test\test.cpp(3) : fatal error C1001: INTERNAL COMPILER ERROR
(compiler file 'msc1.cpp', line 1794)
Please choose the Technical Support command on the Visual C++
Help menu, or open the Technical Support help file for more information
Command line warning D4028 : minimal rebuild failure, reverting to normal build
Error executing cl.exe.
Creating browse info file...
BSCMAKE: warning BK4503 : minor error in .SBR file '.\Debug\test.sbr' ignored

test.exe - 1 error(s), 2 warning(s)

re: Min and max of a POD

Eberhard Schefold wrote:IIRC, there are some MFC and WTL classes that won't work if NOMINMAX is
defined. But for the most part, that'll do, yes.

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re: Min and max of a POD

Fernando Gómez wrote:
If that happens, declare

using std::max;
using std::min;

before including the headers, so they'll find the version from the
standard library.

re: Min and max of a POD

"Gianni Mariani" <gi4nospam@mariani.wswrote:I wonder if and when the 2nd max_val ever gets used at all...?

re: Min and max of a POD

On Jul 4, 5:52*am, "Adem24" <ade...@adem24adem24.org.invalidwrote:when (newv V) is false.

It's the terminating condition.

re: Min and max of a POD

"Gianni Mariani" <owebeeone@gmail.comwrote:And it really works on your machine?
Is the code you posted here correct or are any modification neccessary?
Which compiler and on which platform did you test it?

re: Min and max of a POD

On Jul 4, 10:07 am, "Adem24" <ade...@adem24adem24.org.invalidwrote:yes.
afaict, yes.
I used gcc on cygwin (don't have machine with me so don't know gcc
version).
Also tested it just now on linux boxen with gcc 4.2.2.


Comeau says it's OK as well but has some overflow warnings which are
to be expected since this is a case of find out when the overflow
happens.

Comeau C/C++ 4.3.10.1 (May 29 2008 09:37:15) for
ONLINE_EVALUATION_BETA1
Copyright 1988-2008 Comeau Computing. All rights reserved.
MODE:strict errors C++ C++0x_extensions

"ComeauTest.c", line 4: warning: integer conversion resulted in a
change of sign
static const T newv = V << T(1);
^
detected during:
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=short,
V=(short)16384, W=(short)32767, X=(short)8192,
Y=(short)16383, Z=true]" at line 7
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=short,
V=(short)8192, W=(short)16383, X=(short)4096,
Y=(short)8191, Z=true]" at line 7
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=short,
V=(short)4096, W=(short)8191, X=(short)2048,
Y=(short)4095, Z=true]" at line 7
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=short,
V=(short)2048, W=(short)4095, X=(short)1024,
Y=(short)2047, Z=true]" at line 7
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=short,
V=(short)1024, W=(short)2047, X=(short)512,
Y=(short)1023, Z=true]" at line 7
[ 6 instantiation contexts not shown ]
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=short,
V=(short)8, W=(short)15, X=(short)4, Y=(short)7,
Z=true]"
at line 7
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=short,
V=(short)4, W=(short)7, X=(short)2, Y=(short)3,
Z=true]"
at line 7
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=short,
V=(short)2, W=(short)3, X=(short)1, Y=(short)1,
Z=true]"
at line 7
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=short,
V=(short)1, W=(short)1, X=(short)0, Y=(short)0,
Z=true]"
at line 21
instantiation of class "maxof<T[with T=short]" at line
31

"ComeauTest.c", line 4: warning: integer conversion resulted in a
change of sign
static const T newv = V << T(1);
^
detected during:
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=char,
V='@', W='\177', X=' ', Y='?', Z=true]" at line
7
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=char,
V=' ', W='?', X='\020', Y='\037', Z=true]" at
line 7
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=char,
V='\020', W='\037', X='\b', Y='\017', Z=true]"
at line 7
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=char,
V='\b', W='\017', X='\004', Y='\a', Z=true]" at
line 7
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=char,
V='\004', W='\a', X='\002', Y='\003', Z=true]"
at line 7
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=char,
V='\002', W='\003', X='\001', Y='\001', Z=true]"
at line
7
instantiation of class "max_val<T, V, W, X, Y, Z[with
T=char,
V='\001', W='\001', X='\000', Y='\000', Z=true]"
at line
21
instantiation of class "maxof<T[with T=char]" at line 32