char * to bool

[Travis]

I'm curious what the most reliable way to convert a char * (or a char
for that matter) to a bool is.

It's safe to assume that char * will be either '0' and or '1' and I
want the bool set accordingly.

I'm seeing stuff (from others) like this :

bool myBool = (char)atoi(myCh arPtr);

[Travis]

Re: char * to bool

On Jul 12, 4:59 pm, Travis <travis.bow...@ gmail.comwrote:

I'm curious what the most reliable way to convert a char * (or a char
for that matter) to a bool is.
>
It's safe to assume that char * will be either '0' and or '1' and I
want the bool set accordingly.
>
I'm seeing stuff (from others) like this :
>
bool myBool = (char)atoi(myCh arPtr);

Also to be noted, I also see

bool myBool = !( (char)atoi(myCh arPtr) );

I know ! is a bitwise NOT so how does that work against a char? It's
flipping all the bits and then the bool is determined how? Based on
the value of the lowest bit?

[David Harmon]

Re: char * to bool

On Thu, 12 Jul 2007 23:59:06 -0000 in comp.lang.c++, Travis
<travis.bowers@ gmail.comwrote,

>I'm curious what the most reliable way to convert a char * (or a char
>for that matter) to a bool is.

All methods that work are equally reliable, no?

>It's safe to assume that char * will be either '0' and or '1' and I
>want the bool set accordingly.

bool result = the_char != '0';
bool result = *char_ptr != '0';

>I'm seeing stuff (from others) like this :
>
>bool myBool = (char)atoi(myCh arPtr);

Insane.

[Robert Bauck Hamar]

Re: char * to bool

Travis wrote:

On Jul 12, 4:59 pm, Travis <travis.bow...@ gmail.comwrote:

>I'm curious what the most reliable way to convert a char * (or a char
>for that matter) to a bool is.

Depends on what you want.

>It's safe to assume that char * will be either '0' and or '1' and I
>want the bool set accordingly.

You mean that the char pointed to is '0' or '1'? Like

char a = '0';
char *p = &a;

bool b = *p != '0';

b will be true if a is not '0', and false if a == '0'.

>I'm seeing stuff (from others) like this :
>>
>bool myBool = (char)atoi(myCh arPtr);

atoi tries to convert a sequence of numeric characters in a C style string
to an int. The cast transforms this result to a char. bool would be true if
the value returned fits into a bool and is nonzero or there is no numbers
at the beginning of the string (except whitespace). It would be false if
the value is zero, and you would have a bug if it doesn't fit into a char.

Also to be noted, I also see
>
bool myBool = !( (char)atoi(myCh arPtr) );
>
I know ! is a bitwise NOT so how does that work against a char?

No, it's a boolean not. !true == false, and !false == true. A char is
nothing more than an integer in memory, so a value different from 0
converts to true, and a 0 converts to false.

It's
flipping all the bits and then the bool is determined how? Based on
the value of the lowest bit?

No. ! converts its operand to a bool by the rule I sketched above, and then
flips the truth value.

--
rbh

[Zachary Turner]

Re: char * to bool

On Jul 12, 7:00 pm, Travis <travis.bow...@ gmail.comwrote:

bool myBool = !( (char)atoi(myCh arPtr) );
>
I know ! is a bitwise NOT so how does that work against a char? It's
flipping all the bits and then the bool is determined how? Based on
the value of the lowest bit?

You're thinking of ~ (tilde). ! is a logical not. !0 = true, and !
anything else = false

[Travis]

Re: char * to bool

On Jul 12, 8:19 pm, Zachary Turner <divisorthe...@ gmail.comwrote:

On Jul 12, 7:00 pm, Travis <travis.bow...@ gmail.comwrote:
>

bool myBool = !( (char)atoi(myCh arPtr) );

>

I know ! is a bitwise NOT so how does that work against a char? It's
flipping all the bits and then the bool is determined how? Based on
the value of the lowest bit?

>
You're thinking of ~ (tilde). ! is a logical not. !0 = true, and !
anything else = false

Ah you're right. Thanks.

Doing something like bool myBool = myChar != '0' makes sense.

Thanks everyone.

[Zachary Turner]

Re: char * to bool

On Jul 13, 11:09 am, Travis <travis.bow...@ gmail.comwrote:

On Jul 12, 8:19 pm, Zachary Turner <divisorthe...@ gmail.comwrote:
>

On Jul 12, 7:00 pm, Travis <travis.bow...@ gmail.comwrote:

>

bool myBool = !( (char)atoi(myCh arPtr) );

>

I know ! is a bitwise NOT so how does that work against a char? It's
flipping all the bits and then the bool is determined how? Based on
the value of the lowest bit?

>

You're thinking of ~ (tilde). ! is a logical not. !0 = true, and !
anything else = false

>
Ah you're right. Thanks.
>
Doing something like bool myBool = myChar != '0' makes sense.
>
Thanks everyone.

Yes, but please use parentehses :(