How to wrap a C++ class with a templated constructor

General Usage
1

I’m trying to wrap the fastjet library in C++, using CxxWrap.
I’ve been trying to figure out how to wrap a templated constructor for this class, but I’m failing.
My attempt to just let the compiler figure this out is not met favorably. Is this currently possible? @barche

julia: /afs/desy.de/user/j/jstrube/.julia/packages/CxxWrap/Ho7vF/deps/usr/include/jlcxx/type_conversion.hpp:325: static jl_datatype_t* jlcxx::static_type_mapping<SourceT, Enable>::julia_type() [with SourceT = std::vector<fjcore::PseudoJet>; Enable = void; jl_datatype_t = _jl_datatype_t]: Assertion `type_pointer() != nullptr' failed.

signal (6): Aborted
in expression starting at /afs/desy.de/user/j/jstrube/.julia/dev/FastJet/src/FastJet.jl:9
gsignal at /lib64/libc.so.6 (unknown line)
abort at /lib64/libc.so.6 (unknown line)
__assert_fail_base at /lib64/libc.so.6 (unknown line)
__assert_fail at /lib64/libc.so.6 (unknown line)
_ZN5jlcxx19static_type_mappingISt6vectorIN6fjcore9PseudoJetESaIS3_EEvE10julia_typeEv at /afs/desy.de/user/j/jstrube/.julia/dev/FastJet/deps/usr/lib/libfastjetwrap.so (unknown line)
_ZN5jlcxx10julia_typeISt6vectorIN6fjcore9PseudoJetESaIS3_EEEEP14_jl_datatype_tv at /afs/desy.de/user/j/jstrube/.julia/dev/FastJet/deps/usr/lib/libfastjetwrap.so (unknown line)
_ZN5jlcxx6detail14argtype_vectorIJRKSt6vectorIN6fjcore9PseudoJetESaIS4_EERKNS3_13JetDefinitionEEEES2_IP14_jl_datatype_tSaISD_EEv at /afs/desy.de/user/j/jstrube/.julia/dev/FastJet/deps/usr/lib/libfastjetwrap.so (unknown line)
_ZNK5jlcxx15FunctionWrapperIP11_jl_value_tJRKSt6vectorIN6fjcore9PseudoJetESaIS5_EERKNS4_13JetDefinitionEEE14argument_typesEv at /afs/desy.de/user/j/jstrube/.julia/dev/FastJet/deps/usr/lib/libfastjetwrap.so (unknown line)
register_julia_module at /afs/desy.de/user/j/jstrube/.julia/packages/CxxWrap/jLyxA/deps/usr/lib/libcxxwrap_julia.so (unknown line)
register_julia_module at /afs/desy.de/user/j/jstrube/.julia/packages/CxxWrap/jLyxA/src/CxxWrap.jl:151 [inlined]
readmodule at /afs/desy.de/user/j/jstrube/.julia/packages/CxxWrap/jLyxA/src/CxxWrap.jl:378
wrapmodule at /afs/desy.de/user/j/jstrube/.julia/packages/CxxWrap/jLyxA/src/CxxWrap.jl:384
jl_fptr_trampoline at /buildworker/worker/package_linux64/build/src/gf.c:1829
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2182
do_call at /buildworker/worker/package_linux64/build/src/interpreter.c:324
eval_value at /buildworker/worker/package_linux64/build/src/interpreter.c:428
eval_stmt_value at /buildworker/worker/package_linux64/build/src/interpreter.c:363 [inlined]
eval_body at /buildworker/worker/package_linux64/build/src/interpreter.c:686
and so on...
2

A workaround is here libcxxwrap-julia/types.cpp at main · JuliaInterop/libcxxwrap-julia · GitHub .

3

I don’t understand how this solves my problem.
I know how to implement a method. I don’t know how to implement the templated constructor.

I guess I could write a factory method, give it some other name and just return the type…

4

The problem is the std::vector<PsudoJet>. You would need to either map it, since CxxWrap doesn’t (yet?) provide support for standard containers, or work around it by creating a constructor that takes an ArrayRef like the function @groot suggested. Note that in the context of issue 112 I am looking at making ArrayRef more user friendly. Also, when creating a factory method you can just name it the same as the type and it will look like an outer constructor to Julia.

5

Ah. Thanks for clarifying. Now that makes sense.
And thanks for the suggestion regarding the name of the factory method. I was hoping something like that would work, so I was going to try that anyway, but great that you’re confirming that.

6

Forgot to add in my previous message: you can decipher the types in the error like this:

c++filt -t _ZN5jlcxx19static_type_mappingISt6vectorIN6fjcore9PseudoJetESaIS3_EEvE10julia_typeEv

which yields:

jlcxx::static_type_mapping<std::vector<fjcore::PseudoJet, std::allocator<fjcore::PseudoJet> >, void>::julia_type()