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I encountered the following code in Bruce Eckel's online book. Can you
please clarify what "const char* const data;" means? Thanks
//: C01:MyError.cpp {RunByHand}

class MyError {
const char* const data;
public:
MyError(const char* const msg = 0) : data(msg) {}
};

void f() {
// Here we "throw" an exception object:
throw MyError("something bad happened");
}

int main() {
// As you'll see shortly, we'll want a "try block" here:
f();
} ///:~

"Last Timer" <> wrote in message
news: ups.com...
> I encountered the following code in Bruce Eckel's online book. Can you
> please clarify what "const char* const data;" means?

Doesn't the book explain it?

> //: C01:MyError.cpp {RunByHand}
>
> class MyError {
> const char* const data;

This means that the data member 'data' is a const
pointer to a const type 'char' object. I.e. neither
the pointer nor what it points to may be modified.
(If you try, your compiler should complain).

-Mike

On 30 Jan 2005 11:31:14 -0800 in comp.lang.c++, "Last Timer"
<> wrote,
>please clarify what "const char* const data;" means? Thanks

The first "const" means the characters pointed to cannot be changed
via this pointer. The second one means the pointer value cannot be
changed.

Last Timer wrote:
> I encountered the following code in Bruce Eckel's online book. Can you
> please clarify what "const char* const data;" means? Thanks

Pointers have two attributes that can be constant:
the content of the pointer and the object {date} it
points to.

Many people say that reading from right to left
is easier.
const char * const data;
^ ^-- The pointer is constant.
|-- The data is constant.

When the pointer is constant, it cannot point
to other objects. When the data is constant,
the data cannot be modified by dereferencing
the pointer.

--
Thomas Matthews

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Thanks for your kind replies. Do you read it Left to Right or vice
versa to determine "first" and "second"?

The C++ for Dummies saz on pg 63

const char * pcc="This is a constant string";
char * const cpc="tjhis is also a string";
*pcc='a'; //illegal
*cpc ='b';//legal
pcc="another string" ; //legal
cpc="another string"; illegal

I'm trying to develop a mnemonic to remember these. Instead of rote
learning may be someone can help me figure this out logically.
Thanks again.

"Last Timer" <> wrote in message
news: oups.com...
> Thanks for your kind replies. Do you read it Left to Right or vice
> versa to determine "first" and "second"?
>
> The C++ for Dummies saz on pg 63
>
> const char * pcc="This is a constant string";
> char * const cpc="tjhis is also a string";
> *pcc='a'; //illegal
> *cpc ='b';//legal
> pcc="another string" ; //legal
> cpc="another string"; illegal
>
> I'm trying to develop a mnemonic to remember these. Instead of rote
> learning may be someone can help me figure this out logically.

http://www.ericgiguere.com/articles/...larations.html
Yes, it's about C, but applies to C++ as well. (But of course it
won't cover the 'C++-only' stuff such as class members, etc.
I don't know of a web link for that, but this one should give you
a good start.)

Also, google for a utility called 'cdecl', which can take
a C declaration and translate it to English. It's available
for most platforms, and is supplied with some.

-Mike