Hi you C++ experts out here. This is not a JUCE-specific question, but maybe someone has an idea. For some reasons discussed somewhere else, I’m building my own set of sample buffer classes. I’m using a lot of template stuff for this and I basically have four sample buffer classes, declared like this:
template <typename SampleType>
class TypeASampleBufferRealValued
{
// all member functions you need here
{
template <typename SampleType>
class TypeASampleBufferComplexValued
{
// all member functions you need here
{
template <typename SampleType>
class TypeBSampleBufferRealValued
{
// all member functions you need here
{
template <typename SampleType>
class TypeBSampleBufferComplexValued
{
// all member functions you need here
{
Now I’d like to be able to write templated DSP classes that accept some of this sample buffers. Lets say I have this one:
template <typename SampleType>
class MyDSPClass
{
template <typename BufferType>
void processBuffer (BufferType& buffer)
{
// here I want to check at compile time if for an example BufferType is either
// TypeASampleBufferComplexValued<SampleType> or TypeBSampleBufferComplexValued<SampleType>
}
}
You see from my comment in the processBuffer function what I want to achieve. So I thought writing a little helper class like this could be helpful:
template <typename SampleType>
struct IsSampleBuffer
{
template <typename BufferType>
static constexpr bool real (BufferType&)
{
return std::is_same<BufferType, TypeASampleBufferRealValued<SampleType>>::value ||
std::is_same<BufferType, TypeBSampleBufferRealValued<SampleType>>::value;
}
template <typename BufferType>
static constexpr bool complex (BufferType&)
{
return std::is_same<BufferType, TypeASampleBufferComplexValued<SampleType>>::value ||
std::is_same<BufferType, TypeBSampleBufferComplexValued<SampleType>>::value;
}
template <typename BufferType>
static constexpr bool complexOrReal (BufferType&)
{
return std::is_same<BufferType, TypeASampleBufferRealValued<SampleType>>::value ||
std::is_same<BufferType, TypeBSampleBufferRealValued<SampleType>>::value ||
std::is_same<BufferType, TypeASampleBufferComplexValued<SampleType>>::value ||
std::is_same<BufferType, TypeBSampleBufferComplexValued<SampleType>>::value;
}
};
I’d like to use it like that
template <typename SampleType>
class MyDSPClass
{
template <typename BufferType>
void processBuffer (BufferType& buffer)
{
static_assert (IsSampleBuffer<SampleType>::complex (buffer), "Only complex sample buffers supported");
}
}
However clang tells me Error:(126, 65) static_assert expression is not an integral constant expression. I don’t really see why this expression could not be evaluated at compile time and therefore why this is not an integral constant expression. Did I miss anything? Can this be done better? Any constexpr gurus out here? Any help appreciated 