So the solution for option E with preprocessor support could be   [Phases: https://eel.is/c++draft/lex.phases ]   In Phase 3, when the decomposition into preprocessor tokens happens, the F or X string could be parsed and decomposed into a macro call with reordering of the format string and the {} parameters.   [Separation into preprocessing tokens: https://eel.is/c++draft/lex.pptoken ]     In Phase 4 that internal macro would create a call to std::format for F strings and a comma separated list for X strings and all other macro calls and preprocessor symbol expansions are done for the (previously curly embraced {} ) parameters.         -----Ursprüngliche Nachricht----- Von:Jens Maurer <jens.maurer_at_[hidden]> Gesendet:Mo 16.10.2023 17:19 Betreff:Re: [std-proposals] Supporting f-strings in C++: draft-R1 An:std-proposals_at_[hidden]; CC:Sebastian Wittmeier <wittmeier_at_[hidden]>; On 16/10/2023 15.47, Sebastian Wittmeier via Std-Proposals wrote: > How do F strings react, when they are concatenated out of different types of strings? Does each F one of them have to be complete? Or can a F be mixed with a normal string and the concatenation has to be complete? I'd like to point out that preprocessor tokenization happens in phase 3, macros are expanded in phase 4, and strings are concatenated in phases 5 and 6. See [lex.phases] for details. In which phase are these F or X strings supposed to be turned into something else that presumably ends up as a phase 7 C++ expression performing some formatting when evaluated? Jens