As we have seen, some types of SV deliberately build on and extend the structure of others. The SV code is written to attempt to provide an object-oriented style of programming inside C, and it is fair to say that some SV "classes" inherit from others. In the compiler module B, we see these inheritance relationships spelt out:
@B::PV::ISA = 'B::SV'; @B::IV::ISA = 'B::SV'; @B::NV::ISA = 'B::IV'; @B::RV::ISA = 'B::SV'; @B::PVIV::ISA = qw(B::PV B::IV); @B::PVNV::ISA = qw(B::PV B::NV); @B::PVMG::ISA = 'B::PVNV'; @B::PVLV::ISA = 'B::PVMG'; @B::BM::ISA = 'B::PVMG'; @B::AV::ISA = 'B::PVMG'; @B::GV::ISA = 'B::PVMG'; @B::HV::ISA = 'B::PVMG'; @B::CV::ISA = 'B::PVMG'; @B::IO::ISA = 'B::PVMG'; @B::FM::ISA = 'B::CV';