Fmt – A Modern Formatting Library | Hacker News Reader

Fmt – A Modern Formatting Library

github.com

44 pointsint_hdlr12 comments

It’s really astonishing how bad <ostream> is. It’s not just one or two problems—the <ostream> interface is just a total disaster. In my mind, fmt is not just a replacement for <ostream>, it’s a replacement for <cstdio>, which is a much higher bar to clear.

https://www.moria.us/articles/iostream-is-hopelessly-broken/

For those who don’t know, much of the fmt library interface has been standardized in C++20 as std::format. It’s a great library, and a very efficient alternative to ostream and friends.

It's great that it's there now but it absolutely amazes me how long some of these features have taken.

Concepts took, what, the best part of 20 years and the end result is just OK. Unless there's something I'm missing the system as standardized in C++20 just seems overcooked - not very elegant while also introducing a lot of new legalese in the standard. The system D uses seems to be much simpler (and more powerful in the sense that it effectively moves template constraints into the library - doesn't require updating as traits change) i.e.

    template<typename T>
      if(constexprConditionOnT<T>)
    void toy(T x) {}

The real power of concepts was the “concept_map” construct. Gaby & Bjarne wanted predicated checking instead of structural checking. Without structural checking there’s no “natural” way in C++ syntax to specify a concept_map. The problem is that predicate checking isn’t that great.

I can send you the turd of a PhD thesis that was left after my doctorate was bombed by the removal of concepts from C++0x.

In case anyone is interested here's brief history of standardizing std::format: http://www.zverovich.net/2019/07/23/std-format-cpp20.html

(C++)

I was wondering that was "modern" about it, given that fmt(1) has been around since 3BSD (1979?).

very different, in just about every way. Type safety, deduced by the compiler instead of the stringly-typed %d and friends for starters.

I know I am a barbarian, but I'll probably just continue to use my own std::string sprintf( const char *fmt, ... ); function as implemented here;

https://github.com/billforsternz/retro-sargon/blob/master/sr...

I kind of think that IEEE 754 (or other binary floating point) to ASCII conversion should be its own project, or else in a language's standard library, since it is quite involved, especially if accuracy is important.

The low level part of that was standardized in C++17 as std::to_chars

https://en.cppreference.com/w/cpp/utility/to_chars

I see that the ostream comparison is cooked. On each iteration they trigger a memory allocation.

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