thousands.h

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#pragma once
// SPDX-FileCopyrightText: 2025 Nessan Fitzmaurice <nzznfitz+gh@icloud.com>
// SPDX-License-Identifier: MIT

 
#include <iostream>
#include <locale>
#include <string>
 
namespace utilities {

struct commas_facet : std::numpunct<char> {
    using numpunct::numpunct;
    char        do_thousands_sep() const override { return ','; }
    std::string do_grouping() const override { return "\003"; }
};
 
// We do our own memory management for the commas_facet (set the refs arg to 1).
static commas_facet our_commas_facet{1};
 
// NOTE: GCC on the Mac (or more accurately GCC's libstdc++) is poor at handling std::locale.
// The only locale it seems to know about is "C" or "POSIX"
// The stdlib for clang (libc++) seems to be much more compliant.
static const std::locale default_locale{"C"};
static const std::locale commas_locale(default_locale, &our_commas_facet);

inline void
imbue_stream_with_commas(std::ios_base& strm = std::cout, bool on = true)
{
    on ? strm.imbue(commas_locale) : strm.imbue(default_locale);
}

inline void
imbue_global_with_commas(bool on = true)
{
    on ? std::locale::global(commas_locale) : std::locale::global(default_locale);
}

inline void
pretty_print_thousands(bool on = true)
{
    imbue_global_with_commas(on);
    imbue_stream_with_commas(std::cout, on);
    imbue_stream_with_commas(std::cerr, on);
    imbue_stream_with_commas(std::clog, on);
}
 
} // namespace utilities