Bessel function

Development
1

I have a strange problem. I need to use the Bessel function of first kind jnf(n, x), which should be available for Windows as _jn(n, x), but the compiler claims that it is not declared in this scope. Did anybody manage to use the Bessel function for a Windows build?

Thanks, Martin

2

OK. After some searching I found a solution, but I am not sure whether this is the correct way. Apparently, with mingw, one can only compile with jn(n, x), when using the compiler option -std=gnu++11 rather than the -std=c++11, which is predefined by the Rack Makefile. Does anybody know whether replacing this option causes some other problems later on, or whether it is acceptable to replace it?

3

Excuse my possible ignorance, but haven’t these been added to C++17?

e.g. std::sph_bessel, std::sph_besself, std::sph_bessell - cppreference.com

4

Yes, but afaik Rack is using only C++11. (see Plugin Development Tutorial - VCV Rack Manual)

5

By the way, it is possible to build your VCV Rack plugin using C++17. That’s what I do with my plugin Sapphire. I believe Surge XT uses C++17 also.

Here’s how to do it. Edit your Makefile to remove the C++11 option and replace it with C++17. Find where it does the include statement for plugin.mk and make the following CXXFLAGS updates before/after it, like this:

# Upgrade to C++17
CXXFLAGS += -std=c++17

# Include the Rack plugin Makefile framework
include $(RACK_DIR)/plugin.mk

# Remove C++11
CXXFLAGS := $(filter-out -std=c++11,$(CXXFLAGS))

Sapphire using C++17 works just fine on all hardware platforms (Windows, Mac, Linux).

2 Likes
6

Thanks. I will experiment with that. At the moment, the gnu++11 seems to do the trick.

7

Yeah, I do that, too.