Tag for C++ std::format library specific questions
This tag should be used (along with the [C++] tag) for questions about std::format library.
Questions tagged [stdformat]
15 questions
35
votes
1 answer
How to use C++20 in CMake project
I want to use the header available in C++20.
I am using the most up-to-date release of CMake.
My CMakeFiles looks like
set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_BUILD_TYPE debug)
set(CMAKE_CXX_FLAGS…
Tak Makoni
- 467
- 1
- 4
- 7
4
votes
1 answer
Exception message with C++20 format
Similar to the this question. Needed throw a exception with a message using printf-like style instead of string cocatenation or iostreams. Using the C++ 20 Formatting Library:
throw std::runtime_error {
std::format("Critical error! Code {}:…
Nico Engels
- 407
- 2
- 12
4
votes
1 answer
is std::format at runtime possible?
Can I use a format string defined at runtime in a std::format?
This seems to say that you can't; that all format strings are a compile-time-only thing. I could have sworn that I did this only a few months ago, maybe it was before the Standard was…
masher
- 3,814
- 4
- 31
- 35
3
votes
1 answer
No header file in /usr/include/c++/*
I want to use std::format from c++20.
Installed g++12, libc++-12-dev, libstdc++-12-dev, but the header file is still missing. Ubuntu 22.04
krespo
- 35
- 2
3
votes
2 answers
std::format pointer error C3615: consteval function 'std::_Compile_time_parse_format_specs' cannot result in a constant expression
How to fix (stdC++20 mode VS2022)
#include
#include
auto dump(int *p)
{
std::string resultstring = std::format(" p points to address {:p}", p);
resulting in:
error C3615: consteval function…
GeePokey
- 159
- 7
2
votes
1 answer
Inserting Characters in Placeholder in `std::format`
In the C++20 library, is it possible to insert characters in a placeholder, so that those characters behave like a part of the passed parameter?
For example, I have the following statement:
std::format("Test '{:<{}}'", 123, 5)
which…
ENIAC
- 813
- 1
- 8
- 19
2
votes
1 answer
Is std::format going to work with things like ICU UnicodeString?
Rather than a long preamble, here is my core question, up front. The paragraphs below explain in more detail.
Is there a template parameter in std::format (or fmt) that will allow me to format into ICU UnicodeStrings?, or perhaps into something like…
Rob N
- 15,024
- 17
- 92
- 165
2
votes
1 answer
Can I call std::format with a consteval std::array as the format string?
I have a consteval std::array that contains a format string:
consteval std::array make_consteval_format_string()
{
return std::array {'{', '}', '\n'}; // "{}\n"
}
I can convert this array to std::string_view and invoke…
Elad Maimoni
- 3,703
- 3
- 20
- 37
1
vote
0 answers
c++ std::format from module crashes the program
I have a simple program in main.cpp file:
import ;
import ;
int main() {
std::cout << std::format("{}, {}!", "Hello", "world") << std::endl;
}
It uses iostream and format modules which are compiled with
g++ -std=c++20…
Sun of A beach
- 171
- 1
- 10
1
vote
1 answer
How could I extend a format-spec for existing type (eg float) in C++?
I want to extend formatting options for floating-point type, preferably preserving some of the existing options. For instance, I want to add a new type specifier for the measurements with units to write like this std::format({:.5mm}, 0.05f) and get…
Andrew
- 311
- 1
- 7
1
vote
1 answer
std::format error : basic_format_string' is not a constant expression
Here is the code
m_state.script_file(
( std::filesystem::path{ xorstr_( "magma/luas" ) } /= name ).string( ),
[ & ] ( lua_State* const state, sol::protected_function_result result ) {
if (…
Jerry Ho
- 11
- 1
1
vote
2 answers
How to forward formatting information from std::format
I am trying to use c++20's std::format on msvc.
When I try to define a format for a custom type Person, I hope to be able to use the external std::format("{:x}{:*^10}", person) in "{:x}{:*^10}" is forwarded to std::formatter::fomat and used…
Ne C
- 99
- 6
0
votes
1 answer
Using std::format with custom types
I'm trying to compile an example from C++20 STL Cookbook. The example is about creating a specialization for std::formatter for a custom type, but I'm getting compilation error. I'm using GCC 13.1 on Windows.
I'm getting the same issue on compiler…
Aamir
- 1,974
- 1
- 14
- 18
0
votes
1 answer
how to separate $n and numbers in std::regex_replace?
I have such a regex pattern:
string text = "ekwfwierflwi..DATE..wdwedwd"
const string pattern = "([\s\S]*)(DATE)([\s\S]*)";
Then I hope to replace date to a number sequence:
const string format = fmt::format("$1{}$3", "2024-04.05…
barbyQAQ
- 45
- 5
0
votes
1 answer
How do I preserve inter-string null characters in std::format string
In an attempt to refactor this code:
static const auto opf_str = [&]() {
std::string result;
for(auto& e : extension_list) {
result.append(StringUtils::ToUpperCase(e.substr(1)) + " file (*"s + e + ")\0*"s + e + "\0"s);
}
…
Casey
- 10,297
- 11
- 59
- 88