pointers and typedefs
pointers and typedefs
(OP)
Hi there,
I have been struggling for the last days trying to understand one statement made in the book I am reading at the moment (C++ Primer, 5th Ed, page 129)
It tries to explain pointers and typedefs and, for that, gives this bit of code:
typedef string *pstring;
const pstring cstr;
Saying (literally) then: "...what is the type of cstr? The simple answer is that it is a pointer to a const pstring...". After some explanation it concludes then that cstr is a const pointer to a string as well.
OK, I understand at the end cstr is a const pointer to a string (wasn't easy but finally got it), but honestly don't understand why it says it is a pointer to const pstring (note pstring and not strng)...why?? where does the pointer to a pstring come from??
If you could please help me I would be very pleased.
Thanks a lot indeed!!
I have been struggling for the last days trying to understand one statement made in the book I am reading at the moment (C++ Primer, 5th Ed, page 129)
It tries to explain pointers and typedefs and, for that, gives this bit of code:
typedef string *pstring;
const pstring cstr;
Saying (literally) then: "...what is the type of cstr? The simple answer is that it is a pointer to a const pstring...". After some explanation it concludes then that cstr is a const pointer to a string as well.
OK, I understand at the end cstr is a const pointer to a string (wasn't easy but finally got it), but honestly don't understand why it says it is a pointer to const pstring (note pstring and not strng)...why?? where does the pointer to a pstring come from??
If you could please help me I would be very pleased.
Thanks a lot indeed!!
Talk To Other Members
RE: pointers and typedefs
Simple, but wrong.
cstr is a const pstring
Within the declaration itself, there is no pointer, so saying that it's a "pointer to" is just wrong.
But then you have to look back to discover that pstring is really string*, at which point it becomes clear that cstr is a const string *
Sure, the fully resolved declaration is that cstr is a pointer to a const string.
> cstr is a const pointer to a string as well.
Careful, "const pointer" and "pointer to const" are both valid terms, but they don't mean the same thing.
CODE
*p = 'a'; // modifying what it points at is valid
p = &anotherchar; // modifying where it points is not.
CODE
*p = 'a'; // modifying what it points at is invalid
p = &anotherchar; // modifying where it points is fine.
--
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.