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dmitry.sychov@mail.ru
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 Posted: Wed May 17, 2006 2:21 am Post subject: compile time strings of one char |
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Hello,
I need to create and get access to the compile time string of 'N'
length
where 'N' is the template class argument of type int.
The string should be of one char only.
Here is my solution:
////////////////////////////////////////////////
template <char ch, int n> struct cx_one_char : public cx_one_char<ch,
n-1> {
static const char _ch = ch; };
template <char ch> struct cx_one_char<ch, 0> {
static const char _ch = '\0'; };
int main() {
const char *p_char1 = &cx_one_char<'A', 4>::_ch; // returns "AAAA"
const char *p_char2 = &cx_one_char<'A', 3>::_ch; // returns "AAA"
const char *p_char3 = &cx_one_char<'A', 5>::_ch; // returns "AAAAA"
const char *p_char4 = &cx_one_char<'A', 10>::_ch;
const char *p_char5 = &cx_one_char<'A', 0>::_ch; // returns ""
const char *p_char6 = &cx_one_char<'A', 1>::_ch; // returns "A"
return 0;
}
////////////////////////////////////////////////
While it works on MS VC 2005 there is no doubt that it relies on
several things
like char alignment of 1, so I guess it is a bit dangerous.
Does more robust solution exist?
Thank you, Dmitry
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Bob Hairgrove
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| Posted: Sat May 20, 2006 10:21 pm Post subject: Re: compile time strings of one char |
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On 16 May 2006 21:48:50 -0400, "dmitry.sychov (AT) mail (DOT) ru"
<dmitry.sychov (AT) mail (DOT) ru> wrote:
| Quote: | Hello,
I need to create and get access to the compile time string of 'N'
length
where 'N' is the template class argument of type int.
The string should be of one char only.
Here is my solution:
////////////////////////////////////////////////
template <char ch, int n> struct cx_one_char : public cx_one_char<ch,
n-1> {
static const char _ch = ch; };
template <char ch> struct cx_one_char<ch, 0> {
static const char _ch = '\0'; };
int main() {
const char *p_char1 = &cx_one_char<'A', 4>::_ch; // returns "AAAA"
const char *p_char2 = &cx_one_char<'A', 3>::_ch; // returns "AAA"
const char *p_char3 = &cx_one_char<'A', 5>::_ch; // returns "AAAAA"
const char *p_char4 = &cx_one_char<'A', 10>::_ch;
const char *p_char5 = &cx_one_char<'A', 0>::_ch; // returns ""
const char *p_char6 = &cx_one_char<'A', 1>::_ch; // returns "A"
return 0;
}
////////////////////////////////////////////////
While it works on MS VC 2005 there is no doubt that it relies on
several things
like char alignment of 1, so I guess it is a bit dangerous.
Does more robust solution exist?
|
I don't think so, not as a template. You would always be relying on
implementation-defined behavior with this, according to the C++
standard, because each compiler can add padding between its members as
it chooses. And it is also implementation-defined where it stores
static objects of a class.
Is it really necessary to have this as a template?
--
Bob Hairgrove
NoSpamPlease (AT) Home (DOT) com
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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