How to implement this?

**John Harrison** · Jul 22 '05, 08:26 AM

Re: How to implement this?

"ad" <adconn@168.com > wrote in message
news:5KGbc.1731 7$vo5.530939@bg tnsc05-news.ops.worldn et.att.net...[color=blue]
> Use a variable of char type and each bit of it indicates if a button is
> pressed or not. For example,
>
> 0010010
>
> tells that 3rd and 7th buttons are pressed down.
>
> How to set bit to to 1 or 0 in C++? How to check to see if the 6th bit is
> set to 1 or 0?
>
> Thanks!
>
>[/color]

x |= (1 << n); // set bit n to 1

x &= ~(1 << n); // set bit n to 0

if (x&(1 << n)) // true if bit n is 1

john

**John Harrison** · Jul 22 '05, 08:26 AM

Re: How to implement this?

"ad" <adconn@168.com > wrote in message
news:5KGbc.1731 7$vo5.530939@bg tnsc05-news.ops.worldn et.att.net...[color=blue]
> Use a variable of char type and each bit of it indicates if a button is
> pressed or not. For example,
>
> 0010010
>
> tells that 3rd and 7th buttons are pressed down.
>
> How to set bit to to 1 or 0 in C++? How to check to see if the 6th bit is
> set to 1 or 0?
>
> Thanks!
>
>[/color]

x |= (1 << n); // set bit n to 1

x &= ~(1 << n); // set bit n to 0

if (x&(1 << n)) // true if bit n is 1

john

**John Harrison** · Jul 22 '05, 08:26 AM

Re: How to implement this?

> >[color=blue][color=green]
> > 0010010
> >
> > tells that 3rd and 7th buttons are pressed down.
> >[/color][/color]

Actually to me that looks like the 1st and 4th buttons

0000001 // zeroth button
0000010 // first button
0000100 // second button

etc.

I'm not trying to quibble semantics, but read my previous reply in light of
how I define zeroth bit, first bit, second bit etc.

john

**John Harrison** · Jul 22 '05, 08:26 AM

Re: How to implement this?

> >[color=blue][color=green]
> > 0010010
> >
> > tells that 3rd and 7th buttons are pressed down.
> >[/color][/color]

Actually to me that looks like the 1st and 4th buttons

0000001 // zeroth button
0000010 // first button
0000100 // second button

etc.

I'm not trying to quibble semantics, but read my previous reply in light of
how I define zeroth bit, first bit, second bit etc.

john

**Till Crueger** · Jul 22 '05, 08:26 AM

Re: How to implement this?

On Sat, 03 Apr 2004 22:17:37 +0000, ad wrote:
[color=blue]
> Use a variable of char type and each bit of it indicates if a button is
> pressed or not. For example,
>
> 0010010
>
> tells that 3rd and 7th buttons are pressed down.
>
> How to set bit to to 1 or 0 in C++? How to check to see if the 6th bit
> is set to 1 or 0?[/color]

Define the Flags for the buttons you need. Something like

#define FIRST 1
#define SECOND 2
#define THIRD 4

[...]

then you can simply do an AND with the variable you want to check, and see
wether the result is zero or not. For setting you can do an OR.

Alternatively to the defines you could produce an array which will contain
the appropriate flags.

Till

--
Please add "Salt and Peper" to the subject line to bypass my spam filter

**Till Crueger** · Jul 22 '05, 08:26 AM

Re: How to implement this?

On Sat, 03 Apr 2004 22:17:37 +0000, ad wrote:
[color=blue]
> Use a variable of char type and each bit of it indicates if a button is
> pressed or not. For example,
>
> 0010010
>
> tells that 3rd and 7th buttons are pressed down.
>
> How to set bit to to 1 or 0 in C++? How to check to see if the 6th bit
> is set to 1 or 0?[/color]

Define the Flags for the buttons you need. Something like

#define FIRST 1
#define SECOND 2
#define THIRD 4

[...]

then you can simply do an AND with the variable you want to check, and see
wether the result is zero or not. For setting you can do an OR.

Alternatively to the defines you could produce an array which will contain
the appropriate flags.

Till

--
Please add "Salt and Peper" to the subject line to bypass my spam filter

**Siemel Naran** · Jul 22 '05, 08:27 AM

Re: How to implement this?

"Till Crueger" <TillFC@gmx.net > wrote in message
news:c4ng1l$nq8 $1@f1node01.rhr z.uni-
[color=blue]
> #define FIRST 1
> #define SECOND 2
> #define THIRD 4[/color]

Why not const int?

[color=blue]
> then you can simply do an AND with the variable you want to check, and see
> wether the result is zero or not. For setting you can do an OR.[/color]

How about flipping a bit? For that we can use exclusive or, for which the
symbol is ^. Please let me know if this is correct.

// suppose a byte is 4 bits, CHAR_BITS = 4
int a=0x03 // 0011
a ^= 0x01; // 0011 ^ 0001 = 0010
a ^= 0x01; // 0010 ^ 0001 = 0011

**Siemel Naran** · Jul 22 '05, 08:27 AM

Re: How to implement this?

"Till Crueger" <TillFC@gmx.net > wrote in message
news:c4ng1l$nq8 $1@f1node01.rhr z.uni-
[color=blue]
> #define FIRST 1
> #define SECOND 2
> #define THIRD 4[/color]

Why not const int?

[color=blue]
> then you can simply do an AND with the variable you want to check, and see
> wether the result is zero or not. For setting you can do an OR.[/color]

How about flipping a bit? For that we can use exclusive or, for which the
symbol is ^. Please let me know if this is correct.

// suppose a byte is 4 bits, CHAR_BITS = 4
int a=0x03 // 0011
a ^= 0x01; // 0011 ^ 0001 = 0010
a ^= 0x01; // 0010 ^ 0001 = 0011

**Old Wolf** · Jul 22 '05, 08:27 AM

Re: How to implement this?

"John Harrison" <john_andronicu s@hotmail.com>:[color=blue]
> "ad" <adconn@168.com > wrote:[color=green]
> > How to set bit to to 1 or 0 in C++? How to check to see if the 6th bit is
> > set to 1 or 0?[/color]
>
> x |= (1 << n); // set bit n to 1
>
> x &= ~(1 << n); // set bit n to 0
>
> if (x&(1 << n)) // true if bit n is 1[/color]

These should probably be 1UL instead of 1, because of the case where
x is [unsigned] 'long' and sizeof(long) > sizeof(int).

**Old Wolf** · Jul 22 '05, 08:27 AM

Re: How to implement this?

"John Harrison" <john_andronicu s@hotmail.com>:[color=blue]
> "ad" <adconn@168.com > wrote:[color=green]
> > How to set bit to to 1 or 0 in C++? How to check to see if the 6th bit is
> > set to 1 or 0?[/color]
>
> x |= (1 << n); // set bit n to 1
>
> x &= ~(1 << n); // set bit n to 0
>
> if (x&(1 << n)) // true if bit n is 1[/color]

These should probably be 1UL instead of 1, because of the case where
x is [unsigned] 'long' and sizeof(long) > sizeof(int).

**Rolf Magnus** · Jul 22 '05, 08:27 AM

Re: How to implement this?

Siemel Naran wrote:
[color=blue]
> "Till Crueger" <TillFC@gmx.net > wrote in message
> news:c4ng1l$nq8 $1@f1node01.rhr z.uni-
>[color=green]
>> #define FIRST 1
>> #define SECOND 2
>> #define THIRD 4[/color]
>
> Why not const int?[/color]

Why not enum?
[color=blue][color=green]
>> then you can simply do an AND with the variable you want to check,
>> and see wether the result is zero or not. For setting you can do an
>> OR.[/color]
>
> How about flipping a bit? For that we can use exclusive or, for which
> the symbol is ^. Please let me know if this is correct.
>
> // suppose a byte is 4 bits, CHAR_BITS = 4[/color]

CHAR_BITS is never 4. It is at least 8.
[color=blue]
> int a=0x03 // 0011
> a ^= 0x01; // 0011 ^ 0001 = 0010
> a ^= 0x01; // 0010 ^ 0001 = 0011[/color]

Yes, that's correct.

**Rolf Magnus** · Jul 22 '05, 08:27 AM

Re: How to implement this?

Siemel Naran wrote:
[color=blue]
> "Till Crueger" <TillFC@gmx.net > wrote in message
> news:c4ng1l$nq8 $1@f1node01.rhr z.uni-
>[color=green]
>> #define FIRST 1
>> #define SECOND 2
>> #define THIRD 4[/color]
>
> Why not const int?[/color]

Why not enum?
[color=blue][color=green]
>> then you can simply do an AND with the variable you want to check,
>> and see wether the result is zero or not. For setting you can do an
>> OR.[/color]
>
> How about flipping a bit? For that we can use exclusive or, for which
> the symbol is ^. Please let me know if this is correct.
>
> // suppose a byte is 4 bits, CHAR_BITS = 4[/color]

CHAR_BITS is never 4. It is at least 8.
[color=blue]
> int a=0x03 // 0011
> a ^= 0x01; // 0011 ^ 0001 = 0010
> a ^= 0x01; // 0010 ^ 0001 = 0011[/color]

Yes, that's correct.

**Kevin Goodsell** · Jul 22 '05, 08:28 AM

Re: How to implement this?

Rolf Magnus wrote:[color=blue]
> Siemel Naran wrote:
>[color=green]
>>
>>// suppose a byte is 4 bits, CHAR_BITS = 4[/color]
>
>
> CHAR_BITS is never 4. It is at least 8.
>[/color]

CHAR_BITS could be 4. But CHAR_BIT (at least, the CHAR_BIT that is
#defined in <climits>) cannot be. ;)

I'm sure he knows it cannot actually be 4. I believe he was just
simplifying.

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

**Kevin Goodsell** · Jul 22 '05, 08:28 AM

Re: How to implement this?

Rolf Magnus wrote:[color=blue]
> Siemel Naran wrote:
>[color=green]
>>
>>// suppose a byte is 4 bits, CHAR_BITS = 4[/color]
>
>
> CHAR_BITS is never 4. It is at least 8.
>[/color]

CHAR_BITS could be 4. But CHAR_BIT (at least, the CHAR_BIT that is
#defined in <climits>) cannot be. ;)

I'm sure he knows it cannot actually be 4. I believe he was just
simplifying.

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

How to implement this?

How to implement this?

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment