Argument Parsing for Type Stability

[sjkelly]

It seems as though this line is triggering some type instability: https://github.com/JuliaGeometry/TetGen.jl/blob/4ce1bd589ebfc5a3eb14f729ae5f9657274df7d6/src/cppwrapper.jl#L290-L296

One solution towards this is parsing of the arguments to determine the actual type parameters in the tetrahedralize function.