Due to specific IO process on ibm i there's requirement of using display file fields IO.
As follows we need compile time structures for display file values.
After looking at constexpr I've decided to try some cpp + templates solution from here.
The final code for my case looks like this:
MYSRC/MYMOD.CPP
#include "MYSRC/MODINCH"
template <int N>
constexpr_string<N> make_constexpr_string(const char(&a)[N]) {
// Provide a function template to deduce N ^ right here
return constexpr_string<N>(a);
// ^ Forward the parameter to the class template.
};
int main(int argc, char** argv)
{
return 0;
}
MYSRC/MODINCH.H
#include <algorithm>
#define __IBMCPP_TR1__ 1
#include <QSYSINC/STD(array)>
using std::size_t;
template <size_t N> // N is the capacity of my string.
class constexpr_string {
private:
//std::tr1::array<char, N> data_; // Reserve N chars to store anything.
char data_[N];
std::size_t size_; // The actual size of the string.
public:
constexpr constexpr_string(const char(&a)[N]): data_{}, size_(N - 1)
{
for (std::size_t i = 0; i < N; ++i) {
data_[i] = a[i];
}
}
constexpr iterator begin() { return data_; } // Points at the beggining of the storage.
constexpr iterator end() { return data_ + size_; } // Points at the end of the stored string.
};
The code above compiles with
CRTCPPMOD MODULE(QTEMP/MYMOD) SRCFILE(MYLIB/MYSRC) SRCMBR(MYMOD)
OPTIMIZE(40) DBGVIEW(*ALL) LANGLVL(*EXTENDED0X)
for both char data_[N]; and std::tr1::array<char, N> data_;
However, when I try to populate instance of constexpr_string like this:
#include "MYSRC/MODINCH"
template <int N>
constexpr_string<N> make_constexpr_string(const char(&a)[N]) {
// Provide a function template to deduce N ^ right here
return constexpr_string<N>(a);
// ^ Forward the parameter to the class template.
};
int main(int argc, char** argv)
{
auto test1 = make_constexpr_string("blabla");
constexpr_string<7> test("blabla");
return 0;
}
error instantly fails compilation with this message
CZP0063(30) The text "constexpr_string" is unexpected. right at the ctor line. For me this looks like compiler can not determine the constexpr keyword in this situation, but why?
Did I messed somewhere in code or this usage just currently unsupported?
Here is the supported features of ibm compiler and the IBM XLC++ supports constexpr as far, as I can deduct from given table.