Is the preprocessor still needed in C++? (2017)
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Is the preprocessor still needed in C++? (2017)
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Re: Is the preprocessor still needed in C++? (2017)
#2How can we replace nested comments? You can't comment out code that contains /* */ in it except with #if 0
Also, why is std::experimental::source_location loc = std::experimental::source_location::current(); loc.line better than __LINE__? what an unreadable monster that is!
Re: Is the preprocessor still needed in C++? (2017)
#3TLDR of the article: the new C++ features can replace some macro usages, but not all.
"With current C++(17), most of the preprocessor use can’t be replaced easily."
"And even then: I think that proper macros, which are part of the compiler and very powerful tools for AST generation, are a useful thing to have. Something like Herb Sutter’s metaclasses, for example. However, I definitely don’t want the primitive text replacement of #define."
Re: Is the preprocessor still needed in C++? (2017)
#4How can we replace nested comments? You can't comment out code that contains /* */ in it except with #if 0 Also, why is std::experimental::source_location loc = std::experimental::source_location::current(); loc.line better than __LINE__? what an unreadable monster that is!
> How can we replace nested comments?
s/^/\/\// (and the reverse) work well for me. It nests.
Re: Is the preprocessor still needed in C++? (2017)
#5How can we replace nested comments? You can't comment out code that contains /* */ in it except with #if 0 Also, why is std::experimental::source_location loc = std::experimental::source_location::current(); loc.line better than __LINE__? what an unreadable monster that is!
> How can we replace nested comments?
you may use multiline string literals
Re: Is the preprocessor still needed in C++? (2017)
#6How can we replace nested comments? You can't comment out code that contains /* */ in it except with #if 0 Also, why is std::experimental::source_location loc = std::experimental::source_location::current(); loc.line better than __LINE__? what an unreadable monster that is!
Presumably it would become
auto loc = std::source_location::current();
Re: Is the preprocessor still needed in C++? (2017)
#7We just need an interpreter that can work on C++ files, supported by the standard.
Something akin to the https://www.python.org/dev/peps/pep-0638/
Code generators/transformers are rare only because it's so hard to actually start.
Too bad https://www.circle-lang.org never took off.
Re: Is the preprocessor still needed in C++? (2017)
#8Just yesterday I had to wrap up offsetof in a macro for use in some pseudo-reflection code
#define MEMBER(C, M) { offsetof(C, M), sizeof(C::M) }
[] (const C& c) { return std::cref(c.m); }
Re: Is the preprocessor still needed in C++? (2017)
#9TBH the length that C++ goes to replace every single use of the preprocessor "just because" is close to zealotry.
Every single "fix" probably requires more lines of code under the hood than the entire preprocessor and in the end you have added tons of additional features to the language to fix problems that (often) don't need fixing.
The preprocessor being a simple text replacement tool is a feature, not a bug, but like every universal tool it requires some common sense to not abuse it.
Re: Is the preprocessor still needed in C++? (2017)
#10We just need an interpreter that can work on C++ files, supported by the standard. Something akin to the https://www.python.org/dev/peps/pep-0638/ Code generators/transformers are rare only because it's so hard to actually start. Too bad https://www.circle-lang.org never took off.
Isn’t that what templates and constexpr are?