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4.2 Type-bound Operators

Type-bound operators are in fact basically just GENERIC procedure bindings and are represented much in the same way as those (see Type-bound Procedures).

They come in two flavours: User-defined operators (like .MYOPERATOR.) are stored in the f2k_derived namespace’s tb_uop_root symtree exactly like ordinary type-bound procedures are stored in tb_sym_root; their symtrees’ names are the operator-names (e.g. ‘myoperator’ in the example). Intrinsic operators on the other hand are stored in the namespace’s array member tb_op indexed by the intrinsic operator’s enum value. Those need not be packed into gfc_symtree structures and are only gfc_typebound_proc instances.

When an operator call or assignment is found that cannot be handled in another way (i.e. neither matches an intrinsic nor interface operator definition) but that contains a derived-type expression, all type-bound operators defined on that derived-type are checked for a match with the operator call. If there’s indeed a relevant definition, the operator call is replaced with an internally generated GENERIC type-bound procedure call to the respective definition and that call is further processed.