How do you create two mutually exclusive yet required options in CLI11?

[Coderx7]

This is a follow-up question from here. It seems this is not [clearly?] discussed in the documentations. so here it is again, How can we have two required mutually exclusive options in CLI11?

[phlptp]

Just in case this has not been answered yet
the way to do this is that the options are placed in an option group.

group=app.add_option_group("subgroup");
group->add_flag("--cpu", isOnCpu, "Run the computation on the CPU")->ignore_case();
    group->add_flag("--gpu", isOnGpu, "Run the computation on the GPU")->ignore_case();

group->require_option(1); 

The require_option(1) will state that 1 and only 1 option from the group is required. Any more or less is an error.