In LoadMesh Tutorial

[Gihong-Yim]

#include <MRMesh/MRMesh.h>
#include <MRMesh/MRMeshLoad.h>
#include <MRMesh/MRMeshSave.h>
#include <MRIOExtras/MRCtm.h>
 
#include <iostream>
 
int main()
{
    // Load mesh
    std::filesystem::path inFilePath = "mesh.stl";
    auto loadRes = MR::MeshLoad::fromAnySupportedFormat( inFilePath );
    if ( loadRes.has_value() )
    {
        std::cerr << loadRes.error() << std::endl;
        return 1;
    }
 
    // Save mesh
    std::filesystem::path outFilePath = "mesh.ply";
    auto saveRes = MR::MeshSave::toAnySupportedFormat( loadRes.value(), outFilePath );
    if ( !saveRes.has_value() )
    {
        std::cerr << saveRes.error() << std::endl;
        return 1;
    }
 
    // More mesh formats are available in the MRIOExtras library
    std::filesystem::path outCtmFilePath = "mesh.ctm";
    saveRes = MR::MeshSave::toCtm( loadRes.value(), outCtmFilePath );
    if ( !saveRes.has_value() )
    {
        std::cerr << saveRes.error() << std::endl;
        return 1;
    }
    
    return 0;
}

"This is a LoadMesh tutorial, but it says if ( loadRes.has_value() ) in the code. Is this a typo?"

[Grantim]

Hello!
Please note that many of meshlib functions return values are Expected<T>

MeshLib/source/MRMesh/MRMeshLoad.h

Lines 142 to 144 in 3d1872e

	/// loads mesh from stream in the format detected from given extension-string (`*.ext`);
	/// important on Windows: in stream must be open in binary mode
	MRMESH_API Expected<Mesh> fromAnySupportedFormat( std::istream& in, const std::string& extension, const MeshLoadSettings& settings = {} );

which is https://github.com/MeshInspector/MeshLib/blob/master/source/MRMesh/MRExpected.h (tl::expected<T> which is a lot like std::expected<T>)

So are valid operations for this type

[Fedr]

Yes, the condition in that example was inverted: it must be if ( !loadRes.has_value() ), and the current version of the example (examples/cpp-examples/MeshLoadSave.dox.cpp) has it fixed. Thanks for spotting it.