Hi all,
Can someone throw some light on the implemetation of bool data
type in C++? I have heard that it is bit based, but want to confirm
this information. Is there any source code where I can look into?
~Thanks,
Ramesh.
13  6999 
On Aug 22, 3:34 pm, a2z <ramesh.hem...@gmail.comwrote:
Hi all,
Can someone throw some light on the implemetation of bool data
type in C++? I have heard that it is bit based, but want to confirm
this information. Is there any source code where I can look into?
~Thanks,
Ramesh.
Not dictated by the c++ standard. sizeof(bool) is also implementation
defined. Given that, implemenations are free to represent them in bit-
representation, as a char, or even as an int, or any other way as they
wish.
-N
Neelesh Bodas wrote:
On Aug 22, 3:34 pm, a2z <ramesh.hem...@gmail.comwrote:
>Hi all,
Can someone throw some light on the implemetation of bool
data type in C++? I have heard that it is bit based, but want to
confirm this information. Is there any source code where I can look
into?
~Thanks,
Ramesh.
Not dictated by the c++ standard. sizeof(bool) is also implementation
defined. Given that, implemenations are free to represent them in bit-
representation, as a char, or even as an int, or any other way as they
wish.
Not sure what you mean by "bit-representation". Every object (even of
type 'bool') has to have its own address, so sizeof(bool) cannot be less
than 1, so a char is a minimal unit to represent a bool value. Please
elaborate if I understood you incorrectly.
V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask
On Aug 22, 4:43 pm, "Victor Bazarov" <v.Abaza...@comAcast.netwrote:
Neelesh Bodas wrote:
On Aug 22, 3:34 pm, a2z <ramesh.hem...@gmail.comwrote:
Hi all,
Can someone throw some light on the implemetation of bool
data type in C++? I have heard that it is bit based, but want to
confirm this information. Is there any source code where I can look
into?
~Thanks,
Ramesh.
Not dictated by the c++ standard. sizeof(bool) is also implementation
defined. Given that, implemenations are free to represent them in bit-
representation, as a char, or even as an int, or any other way as they
wish.
Not sure what you mean by "bit-representation". Every object (even of
type 'bool') has to have its own address, so sizeof(bool) cannot be less
than 1, so a char is a minimal unit to represent a bool value. Please
elaborate if I understood you incorrectly.
Probably I used incorrect terminlogy. By "bit-representation" I was
mentioning the same thing that OP meant by "bit based". In other
words, something to the effect that true and false might be any
specific sequence of bits (say 24 bits = 3 bytes) and defined in any
manner - true is alternate one's and zero's and false is all zeros.
-N
Neelesh Bodas wrote:
On Aug 22, 4:43 pm, "Victor Bazarov" <v.Abaza...@comAcast.netwrote:
>Neelesh Bodas wrote:
>>On Aug 22, 3:34 pm, a2z <ramesh.hem...@gmail.comwrote:
Hi all,
Can someone throw some light on the implemetation of bool
data type in C++? I have heard that it is bit based, but want to
confirm this information. Is there any source code where I can look
into?
>>>~Thanks,
Ramesh.
>>Not dictated by the c++ standard. sizeof(bool) is also
implementation defined. Given that, implemenations are free to
represent them in bit- representation, as a char, or even as an
int, or any other way as they wish.
Not sure what you mean by "bit-representation". Every object (even
of type 'bool') has to have its own address, so sizeof(bool) cannot
be less than 1, so a char is a minimal unit to represent a bool
value. Please elaborate if I understood you incorrectly.
Probably I used incorrect terminlogy. By "bit-representation" I was
mentioning the same thing that OP meant by "bit based". In other
words, something to the effect that true and false might be any
specific sequence of bits (say 24 bits = 3 bytes) and defined in any
manner - true is alternate one's and zero's and false is all zeros.
Ah.. I get it. Yes, the representation in memory is not prescribed,
and sizeof(bool) can be anything the implementation wants. Whatever
the OP meant by "bit based" it can't be sharing bits of the same, say,
char, to represent different objects, however. While 'vector<bool>'
does most likely pack the elements in individual bits, a stand-alone
objects of 'bool' type cannot be packed similarly.
V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask
Victor Bazarov wrote:
Not sure what you mean by "bit-representation". Every object (even of
type 'bool') has to have its own address, so sizeof(bool) cannot be less
than 1, so a char is a minimal unit to represent a bool value.
struct A { int i:2, j:3; };
What are the addresses of i and j?
Juha Nieminen wrote:
Victor Bazarov wrote:
>Not sure what you mean by "bit-representation". Every object (even
of type 'bool') has to have its own address, so sizeof(bool) cannot
be less than 1, so a char is a minimal unit to represent a bool
value.
struct A { int i:2, j:3; };
What are the addresses of i and j?
Why don't you try operator& on those, and you'll find out.
V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask
On Aug 22, 3:19 pm, "Victor Bazarov" <v.Abaza...@comAcast.netwrote:
Neelesh Bodas wrote:
On Aug 22, 4:43 pm, "Victor Bazarov" <v.Abaza...@comAcast.netwrote:
Neelesh Bodas wrote:
On Aug 22, 3:34 pm, a2z <ramesh.hem...@gmail.comwrote:
Hi all,
Can someone throw some light on the implemetation of bool
data type in C++? I have heard that it is bit based, but want to
confirm this information. Is there any source code where I can look
into?
>>~Thanks,
Ramesh.
>Not dictated by the c++ standard. sizeof(bool) is also
implementation defined. Given that, implemenations are free to
represent them in bit- representation, as a char, or even as an
int, or any other way as they wish.
Not sure what you mean by "bit-representation". Every object (even
of type 'bool') has to have its own address, so sizeof(bool) cannot
be less than 1, so a char is a minimal unit to represent a bool
value. Please elaborate if I understood you incorrectly.
Probably I used incorrect terminlogy. By "bit-representation" I was
mentioning the same thing that OP meant by "bit based". In other
words, something to the effect that true and false might be any
specific sequence of bits (say 24 bits = 3 bytes) and defined in any
manner - true is alternate one's and zero's and false is all zeros.
Ah.. I get it. Yes, the representation in memory is not prescribed,
and sizeof(bool) can be anything the implementation wants. Whatever
the OP meant by "bit based" it can't be sharing bits of the same, say,
char, to represent different objects, however. While 'vector<bool>'
does most likely pack the elements in individual bits, a stand-alone
objects of 'bool' type cannot be packed similarly.
V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask- Hide quoted text -
since casting false to int results in zero(really? should I be
certain?)it is simpler to be represented with all bits zero,but for
true I guess it should be all ones:
bool a= false^true;//exert an int bitwise xor operator on bools and
cast to bool
what is the result of the above line?(unfortunately C++ lacks bool
xor)
regards,
FM.
On 2007-08-23 16:38, terminator wrote:
On Aug 22, 3:19 pm, "Victor Bazarov" <v.Abaza...@comAcast.netwrote:
>Neelesh Bodas wrote:
On Aug 22, 4:43 pm, "Victor Bazarov" <v.Abaza...@comAcast.netwrote:
Neelesh Bodas wrote:
On Aug 22, 3:34 pm, a2z <ramesh.hem...@gmail.comwrote:
Hi all,
Can someone throw some light on the implemetation of bool
data type in C++? I have heard that it is bit based, but want to
confirm this information. Is there any source code where I can look
into?
>>>~Thanks,
Ramesh.
>>Not dictated by the c++ standard. sizeof(bool) is also
implementation defined. Given that, implemenations are free to
represent them in bit- representation, as a char, or even as an
int, or any other way as they wish.
>Not sure what you mean by "bit-representation". Every object (even
of type 'bool') has to have its own address, so sizeof(bool) cannot
be less than 1, so a char is a minimal unit to represent a bool
value. Please elaborate if I understood you incorrectly.
Probably I used incorrect terminlogy. By "bit-representation" I was
mentioning the same thing that OP meant by "bit based". In other
words, something to the effect that true and false might be any
specific sequence of bits (say 24 bits = 3 bytes) and defined in any
manner - true is alternate one's and zero's and false is all zeros.
Ah.. I get it. Yes, the representation in memory is not prescribed,
and sizeof(bool) can be anything the implementation wants. Whatever
the OP meant by "bit based" it can't be sharing bits of the same, say,
char, to represent different objects, however. While 'vector<bool>'
does most likely pack the elements in individual bits, a stand-alone
objects of 'bool' type cannot be packed similarly.
V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask- Hide quoted text -
since casting false to int results in zero(really? should I be
certain?)it is simpler to be represented with all bits zero,but for
true I guess it should be all ones:
bool a= false^true;//exert an int bitwise xor operator on bools and
cast to bool
what is the result of the above line?(unfortunately C++ lacks bool
xor)
The standard specifies that a "zero value, null pointer value, or null
member pointer value is converted to false; any other value is converted
to true."
--
Erik Wikström
On Aug 23, 6:53 pm, "Victor Bazarov" <v.Abaza...@comAcast.netwrote:
Juha Nieminen wrote:
Victor Bazarov wrote:
Not sure what you mean by "bit-representation". Every object (even
of type 'bool') has to have its own address, so sizeof(bool) cannot
be less than 1, so a char is a minimal unit to represent a bool
value.
struct A { int i:2, j:3; };
What are the addresses of i and j?
Why don't you try operator& on those, and you'll find out.
I guess you did not notice that struct members are bit fields. So even
if an instance of the struct object is created, u cannot *portably*
find the address of its members which are bit fields.
On 2007-08-23 17:02, Rajesh S R wrote:
On Aug 23, 6:53 pm, "Victor Bazarov" <v.Abaza...@comAcast.netwrote:
>Juha Nieminen wrote:
Victor Bazarov wrote:
Not sure what you mean by "bit-representation". Every object (even
of type 'bool') has to have its own address, so sizeof(bool) cannot
be less than 1, so a char is a minimal unit to represent a bool
value.
struct A { int i:2, j:3; };
What are the addresses of i and j?
Why don't you try operator& on those, and you'll find out.
I guess you did not notice that struct members are bit fields. So even
if an instance of the struct object is created, u cannot *portably*
find the address of its members which are bit fields.
Actually you shall not apply the address-of operator to bit-fields at all.
--
Erik Wikström
Erik Wikström wrote:
On 2007-08-23 17:02, Rajesh S R wrote:
>On Aug 23, 6:53 pm, "Victor Bazarov" <v.Abaza...@comAcast.netwrote:
>>Juha Nieminen wrote:
Victor Bazarov wrote:
Not sure what you mean by "bit-representation". Every object (even
of type 'bool') has to have its own address, so sizeof(bool) cannot
be less than 1, so a char is a minimal unit to represent a bool
value.
struct A { int i:2, j:3; };
What are the addresses of i and j?
Why don't you try operator& on those, and you'll find out.
I guess you did not notice that struct members are bit fields. So even
if an instance of the struct object is created, u cannot *portably*
find the address of its members which are bit fields.
Actually you shall not apply the address-of operator to bit-fields at all.
It was just a note about the original claim "every object has to have
its own address". I was thinking it doesn't apply to bitfields, so they
are not the same type of "objects" as everything else...
On Aug 24, 2:38 am, terminator <farid.mehr...@gmail.comwrote:
bool a= false^true;//exert an int bitwise xor operator on bools and
cast to bool
what is the result of the above line?
The operands of '^' are promoted to int before the
xor operation is evaluated, so it is the same as:
bool a = 0^1;
regardless of internal representation of bool.
(Which must result in 'a' == true).
On Aug 28, 2:38 am, Old Wolf <oldw...@inspire.net.nzwrote:
On Aug 24, 2:38 am, terminator <farid.mehr...@gmail.comwrote:
bool a= false^true;//exert an int bitwise xor operator on bools and
cast to bool
what is the result of the above line?
The operands of '^' are promoted to int before the
xor operation is evaluated, so it is the same as:
bool a = 0^1;
regardless of internal representation of bool.
(Which must result in 'a' == true).
that is what I guess .but can I be sure?
thanks,
FM. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics
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