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determines if it is a signed type

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  determines if it is a signed type asetofsymbols@gmail.com - 2015-05-17 10:07 -0700
    Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-17 18:12 +0100
      Re: determines if it is a signed type asetofsymbols@gmail.com - 2015-05-17 10:34 -0700
        Re: determines if it is a signed type asetofsymbols@gmail.com - 2015-05-17 11:09 -0700
        Re: determines if it is a signed type Kusalananda <kusalananda@example.com> - 2015-05-17 18:22 +0000
          Re: determines if it is a signed type asetofsymbols@gmail.com - 2015-05-17 11:31 -0700
            Re: determines if it is a signed type Kusalananda <kusalananda@example.com> - 2015-05-17 19:59 +0000
    Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-17 13:12 -0700
    Re: determines if it is a signed type Morris Dovey <mrdovey@iedu.com> - 2015-05-17 19:08 -0500
      Re: determines if it is a signed type Morris Dovey <mrdovey@iedu.com> - 2015-05-17 19:46 -0500
      Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-18 01:59 +0100
        Re: determines if it is a signed type Morris Dovey <mrdovey@iedu.com> - 2015-05-17 20:10 -0500
        Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-18 00:37 -0700
          Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-18 21:15 +0100
            Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-18 15:15 -0700
          Re: determines if it is a signed type glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-18 21:51 +0000
            Re: determines if it is a signed type James Kuyper <jameskuyper@verizon.net> - 2015-05-18 18:00 -0400
        Re: determines if it is a signed type glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-18 14:37 +0000
          Re: determines if it is a signed type jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-18 17:09 +0200
            Re: determines if it is a signed type glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-18 18:14 +0000
      Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-18 06:34 +0100
        Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-18 00:43 -0700
          Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-18 13:56 +0100
            Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-18 08:00 -0700
              Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-18 20:35 +0100
                Re: determines if it is a signed type jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-18 23:08 +0200
                  Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-18 22:32 +0100
                    Re: determines if it is a signed type jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-19 00:44 +0200
                      Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-19 00:05 +0100
                        Re: determines if it is a signed type jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-19 01:43 +0200
                          Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-19 01:08 +0100
                            Re: determines if it is a signed type "Bartc" <bartc@freeuk.com> - 2015-05-19 11:33 +0100
                              Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-19 08:15 -0700
                                Re: determines if it is a signed type "Bartc" <bartc@freeuk.com> - 2015-05-19 19:36 +0100
                                  Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-19 11:55 -0700
                            Re: determines if it is a signed type jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-19 11:39 +0200
                              Re: determines if it is a signed type "Bartc" <bartc@freeuk.com> - 2015-05-19 11:44 +0100
                                Re: determines if it is a signed type jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-19 12:11 +0200
                              Re: determines if it is a signed type jadill33@gmail.com - 2015-05-19 05:45 -0700
                                Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-19 15:03 +0100
                                  Re: determines if it is a signed type jadill33@gmail.com - 2015-05-19 08:46 -0700
                                    Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-19 17:08 +0100
                                      Re: determines if it is a signed type jadill33@gmail.com - 2015-05-19 09:52 -0700
                                        Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-19 20:36 +0100
                                          Re: determines if it is a signed type jadill33@gmail.com - 2015-05-20 07:40 -0700
                                            Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-20 23:12 +0100
                                              Re: determines if it is a signed type jadill33@gmail.com - 2015-05-21 13:52 -0700
                                                Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-21 22:48 +0100
                                                  Re: determines if it is a signed type jadill33@gmail.com - 2015-05-22 05:50 -0700
                                                    Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-22 23:14 +0100
                                                      Re: determines if it is a signed type jadill33@gmail.com - 2015-05-26 14:31 -0700
                                            Re: determines if it is a signed type Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-22 23:32 -0700
                                  Re: determines if it is a signed type David Brown <david.brown@hesbynett.no> - 2015-05-20 12:26 +0200
                              Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-19 15:28 +0100
                                Re: determines if it is a signed type raltbos@xs4all.nl (Richard Bos) - 2015-05-23 10:37 +0000
                Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-18 15:21 -0700
                  Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-19 00:04 +0100
                    Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-19 08:03 -0700
                  Re: determines if it is a signed type David Brown <david.brown@hesbynett.no> - 2015-05-19 08:47 +0200
                    Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-19 08:07 -0700
            Re: determines if it is a signed type James Kuyper <jameskuyper@verizon.net> - 2015-05-18 11:28 -0400
      Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-18 00:40 -0700

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#62183 — determines if it is a signed type

 a way for know
 C type T is signed
T a=-1, b;
b=a/2;
if(b==0||b==-1) signed
else.           unsigned
Is it right?
Is there any better way?

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#62185

On 17/05/15 18:07, asetofsymbols@gmail.com wrote:
>   a way for know
>   C type T is signed
> T a=-1, b;
> b=a/2;
> if(b==0||b==-1) signed
> else.           unsigned
> Is it right?
> Is there any better way?

There's a much better way. Look at the definition statement.

-- 
Richard Heathfield
Email: rjh at cpax dot org dot uk
"Usenet is a strange place" - dmr 29 July 1999
Sig line 4 vacant - apply within

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#62189

One other way could be
T a=1;
if(-a<0) signed
else.  Unsigned

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#62190

One other way could be 
T a;
a= -1;
if(a<0) signed 
else  Unsigned

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#62191

On 2015-05-17, asetofsymbols@gmail.com <asetofsymbols@gmail.com> wrote:
> One other way could be
> T a=1;
> if(-a<0) signed
> else.  Unsigned

Did you actually try this?

-- 
:: Andreas  Kusalananda Kahari ::
:: Uppsala  University, Sweden ::
:: a n d r e a s . k a h a r i ::
:: @  i  c  m  . u  u  .  s  e ::

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#62192

Kusalananda  wrote"

On 2015-05-17, asetof...@gmail.com <asetof...@gmail.com> wrote: 
> One other way could be 
> T a=1; 
> if(-a<0) signed 
> else.  Unsigned 


Did you actually try this? 
"
Not i try:
T a;
a= -1;
if(a<0)goto label;

It seems ok in C++, if i define
a conversion routine from
integer to each T type
but would be OT...

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#62196

On 2015-05-17, asetofsymbols@gmail.com <asetofsymbols@gmail.com> wrote:
> Kusalananda  wrote"
>
> On 2015-05-17, asetof...@gmail.com <asetof...@gmail.com> wrote: 
>> One other way could be 
>> T a=1; 
>> if(-a<0) signed 
>> else.  Unsigned 
>
>
> Did you actually try this? 
> "
> Not i try:
> T a;
> a= -1;
> if(a<0)goto label;
>
> It seems ok in C++, if i define
> a conversion routine from
> integer to each T type
> but would be OT...
>

If you tried it in C, you would quite likely notice a warning produced
by the compiler when the unknown type T is unsigned.  It knows when the
type is signed or unsigned at the time of compilation.  Why don't you?


-- 
:: Andreas  Kusalananda Kahari ::
:: Uppsala  University, Sweden ::
:: a n d r e a s . k a h a r i ::
:: @  i  c  m  . u  u  .  s  e ::

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#62197

asetofsymbols@gmail.com writes:
>  a way for know
>  C type T is signed
> T a=-1, b;
> b=a/2;
> if(b==0||b==-1) signed
> else.           unsigned
> Is it right?
> Is there any better way?

Given a numeric type T (presumably a typedef name):

    if ((T)-1 > 0) {
        puts("T is unsigned");
    }
    else if ((T)1 / 2 == 0) {
        puts("T is signed");
    }
    else {
        puts("T is floating-point");
    }

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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#62207

On 5/17/15 12:07 PM, asetofsymbols@gmail.com wrote:
> Is there any better way?

Of course - look at the declaration!

If you’re too lazy to do that, you could try (untested)

#define IS_SIGNED(t) (((t) < 0) || (-(t) < 0) || (~(t) < 0))

-- 
Morris Dovey
http://www.iedu.com/Solar

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#62208

On 5/17/15 7:08 PM, Morris Dovey wrote:
> On 5/17/15 12:07 PM, asetofsymbols@gmail.com wrote:
>> Is there any better way?
>
> Of course - look at the declaration!
>
> If you’re too lazy to do that, you could try
>
> #define IS_SIGNED(t) (((t) < 0) || (-(t) < 0) || (~(t) < 0))

OTOH...

#define IS_SIGNED(t) (((t) < 0) || (-(t) < 0) || (((t) - 1) < 0))

appears to work for floating point as well as integer types :-)

-- 
Morris Dovey
http://www.iedu.com/Solar

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#62209

Morris Dovey <mrdovey@iedu.com> writes:

> On 5/17/15 12:07 PM, asetofsymbols@gmail.com wrote:
>> Is there any better way?
>
> Of course - look at the declaration!
>
> If you’re too lazy to do that, you could try (untested)
>
> #define IS_SIGNED(t) (((t) < 0) || (-(t) < 0) || (~(t) < 0))

Hmm...  Not, I think, 100% portable in that on a ones' complement
machine with "normal" negative zeros, C permits ~t to be zero (i.e. not
< 0).

-- 
Ben.

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#62210

On 5/17/15 7:59 PM, Ben Bacarisse wrote:
> Hmm...  Not, I think, 100% portable in that on a ones' complement
> machine with "normal" negative zeros, C permits ~t to be zero (i.e.
> not < 0).

Yes. I experienced some vague discomfort with what I'd written and got
rid of the '~'. :-)

-- 
Morris Dovey
http://www.iedu.com/Solar

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#62214

Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
> Morris Dovey <mrdovey@iedu.com> writes:
>> On 5/17/15 12:07 PM, asetofsymbols@gmail.com wrote:
>>> Is there any better way?
>>
>> Of course - look at the declaration!
>>
>> If you’re too lazy to do that, you could try (untested)
>>
>> #define IS_SIGNED(t) (((t) < 0) || (-(t) < 0) || (~(t) < 0))
>
> Hmm...  Not, I think, 100% portable in that on a ones' complement
> machine with "normal" negative zeros, C permits ~t to be zero (i.e. not
> < 0).

And it has undefined behavior on a two's-complement system if t is
INT_MIN.

I think it can fail if t is of an unsigned type that promotes to signed
int (I'll check that later).

I had assumed the argument should be a type rather than an expression of
the type.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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#62246

Keith Thompson <kst-u@mib.org> writes:

> Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
>> Morris Dovey <mrdovey@iedu.com> writes:
>>> On 5/17/15 12:07 PM, asetofsymbols@gmail.com wrote:
>>>> Is there any better way?
>>>
>>> Of course - look at the declaration!
>>>
>>> If you’re too lazy to do that, you could try (untested)
>>>
>>> #define IS_SIGNED(t) (((t) < 0) || (-(t) < 0) || (~(t) < 0))
>>
>> Hmm...  Not, I think, 100% portable in that on a ones' complement
>> machine with "normal" negative zeros, C permits ~t to be zero (i.e. not
>> < 0).
>
> And it has undefined behavior on a two's-complement system if t is
> INT_MIN.

How so?

<snip>
-- 
Ben.

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#62252

Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
> Keith Thompson <kst-u@mib.org> writes:
>> Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
>>> Morris Dovey <mrdovey@iedu.com> writes:
>>>> On 5/17/15 12:07 PM, asetofsymbols@gmail.com wrote:
>>>>> Is there any better way?
>>>>
>>>> Of course - look at the declaration!
>>>>
>>>> If you’re too lazy to do that, you could try (untested)
>>>>
>>>> #define IS_SIGNED(t) (((t) < 0) || (-(t) < 0) || (~(t) < 0))
>>>
>>> Hmm...  Not, I think, 100% portable in that on a ones' complement
>>> machine with "normal" negative zeros, C permits ~t to be zero (i.e. not
>>> < 0).
>>
>> And it has undefined behavior on a two's-complement system if t is
>> INT_MIN.
>
> How so?
>
> <snip>

Never mind.  (-(INT_MIN)) has undefined behavior on such a system, but
it's never evaluated because (INT_MIN) < 0 is true.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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#62249

Keith Thompson <kst-u@mib.org> wrote:
> Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
(snip)
>>> #define IS_SIGNED(t) (((t) < 0) || (-(t) < 0) || (~(t) < 0))
(snip)
>> Hmm...  Not, I think, 100% portable in that on a ones' complement
>> machine with "normal" negative zeros, C permits ~t to be zero (i.e. not
>> < 0).
 
> And it has undefined behavior on a two's-complement system if t is
> INT_MIN.

-INT_MIN overflows on a twos-complement machine, but ~INT_MIN doesn't.

But if ~INT_MIN was evaluated as -INT_MIN-1 then, yes, it would
be undefined. No reason to do that, though.
 
> I think it can fail if t is of an unsigned type that promotes to signed
> int (I'll check that later).

-- glen

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#62250

On 05/18/2015 05:51 PM, glen herrmannsfeldt wrote:
> Keith Thompson <kst-u@mib.org> wrote:
>> Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
> (snip)
>>>> #define IS_SIGNED(t) (((t) < 0) || (-(t) < 0) || (~(t) < 0))
> (snip)
>>> Hmm...  Not, I think, 100% portable in that on a ones' complement
>>> machine with "normal" negative zeros, C permits ~t to be zero (i.e. not
>>> < 0).
>  
>> And it has undefined behavior on a two's-complement system if t is
>> INT_MIN.
> 
> -INT_MIN overflows on a twos-complement machine, but ~INT_MIN doesn't.

More importantly, if t is INT_MIN, then (t)<0 doesn't overflow, has a
value of 1, and therefore ensures that neither -(t) nor ~(t) ever gets
evaluated.

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#62219

Ben Bacarisse <ben.usenet@bsb.me.uk> wrote:
> Morris Dovey <mrdovey@iedu.com> writes:
 
>> On 5/17/15 12:07 PM, asetofsymbols@gmail.com wrote:
>>> Is there any better way?

>> Of course - look at the declaration!

>> If you???re too lazy to do that, you could try (untested)

>> #define IS_SIGNED(t) (((t) < 0) || (-(t) < 0) || (~(t) < 0))
 
> Hmm...  Not, I think, 100% portable in that on a ones' complement
> machine with "normal" negative zeros, C permits ~t to be zero (i.e. not
> < 0).

Which reminds me, are there any C compilers for the CDC 6600?

-- glen

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#62221

Le 18/05/2015 16:37, glen herrmannsfeldt a écrit :

> Which reminds me, are there any C compilers for the CDC 6600?
>
> -- glen
>

There we go.

Ahhhhh you remember back then?

1968?

THOSE WERE THE DAYS MY FRIEND

WE THOUGHT THEY WOULD NEVER END

And again we start the specialty of this group...

:-)

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#62236

jacobnavia <jacob@jacob.remcomp.fr> wrote:
> Le 18/05/2015 16:37, glen herrmannsfeldt a écrit :
> 
>> Which reminds me, are there any C compilers for the CDC 6600?

(snip)
(or maybe cross compilers)

> There we go.
 
> Ahhhhh you remember back then?
 
> 1968?

http://livingcomputermuseum.cmail2.com/t/ViewEmail/t/8DABEE59AC800AD5/C0FC513325AE3FFF2540EF23F30FEDED

-- glen

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