refactor: remove dependency on <ranges> header and switch to use an iterator-based copy algorithm

src/core/include/mp-units/bits/core_gmf.h

@@ -39,7 +39,6 @@
 #include <numeric>
 #include <optional>
 #include <random>
-#include <ranges>
 #include <sstream>
 #include <string>
 #include <string_view>

src/core/include/mp-units/bits/text_tools.h

@@ -95,7 +95,7 @@ constexpr Out copy(const symbol_text<N, M>& txt, text_encoding encoding, Out out
 {
   if (encoding == text_encoding::unicode) {
     if constexpr (is_same_v<CharT, char8_t>)
-      return copy(txt.unicode(), out).out;
+      return ::mp_units::detail::copy(txt.unicode().begin(), txt.unicode().end(), out);
     else if constexpr (is_same_v<CharT, char>) {
       for (const char8_t ch : txt.unicode()) *out++ = static_cast<char>(ch);
       return out;
@@ -103,7 +103,7 @@ constexpr Out copy(const symbol_text<N, M>& txt, text_encoding encoding, Out out
       throw std::invalid_argument("Unicode text can't be copied to CharT output");
   } else {
     if constexpr (is_same_v<CharT, char>)
-      return copy(txt.ascii(), out).out;
+      return ::mp_units::detail::copy(txt.ascii().begin(), txt.ascii().end(), out);
     else
       throw std::invalid_argument("ASCII text can't be copied to CharT output");
   }

src/core/include/mp-units/ext/algorithm.h

@@ -31,7 +31,6 @@
 #include <compare>
 #include <initializer_list>
 #include <iterator>
-#include <ranges>
 #endif
 
 namespace mp_units::detail {
@@ -164,44 +163,11 @@ constexpr const T& min(const T& a, const T& b)
   return (b < a) ? b : a;
 }
 
-template<class I, class O>
-struct in_out_result {
-  [[no_unique_address]] I in;
-  [[no_unique_address]] O out;
-
-  template<class I2, class O2>
-    requires std::convertible_to<const I&, I2> && std::convertible_to<const O&, O2>
-  constexpr operator in_out_result<I2, O2>() const&
-  {
-    return {in, out};
-  }
-
-  template<class I2, class O2>
-    requires std::convertible_to<I, I2> && std::convertible_to<O, O2>
-  constexpr operator in_out_result<I2, O2>() &&
-  {
-    return {std::move(in), std::move(out)};
-  }
-};
-
-template<class I, class O>
-using copy_result = in_out_result<I, O>;
-
-template<std::input_iterator I, std::sentinel_for<I> S, std::weakly_incrementable O>
-  requires std::indirectly_copyable<I, O>
-constexpr copy_result<I, O> copy(I first, S last, O result)
+template<class InputIt, class OutputIt>
+constexpr OutputIt copy(InputIt first, InputIt last, OutputIt d_first)
 {
-  for (; first != last; ++first, (void)++result) {
-    *result = *first;
-  }
-  return {std::move(first), std::move(result)};
-}
-
-template<std::ranges::input_range R, std::weakly_incrementable O>
-  requires std::indirectly_copyable<std::ranges::iterator_t<R>, O>
-constexpr copy_result<std::ranges::borrowed_iterator_t<R>, O> copy(R&& r, O result)
-{
-  return ::mp_units::detail::copy(std::ranges::begin(r), std::ranges::end(r), std::move(result));
+  for (; first != last; (void)++first, (void)++d_first) *d_first = *first;
+  return d_first;
 }
 
 }  // namespace mp_units::detail

src/core/include/mp-units/format.h

@@ -319,7 +319,7 @@ class MP_UNITS_STD_FMT::formatter<mp_units::quantity<Reference, Rep>, Char> {
       out = MP_UNITS_STD_FMT::vformat_to(out, locale, f.dimension_format_str_,
                                          MP_UNITS_STD_FMT::make_format_args(q.dimension));
     }
-    void on_text(const Char* begin, const Char* end) const { std::copy(begin, end, out); }
+    void on_text(const Char* begin, const Char* end) const { mp_units::detail::copy(begin, end, out); }
   };
   template<typename OutputIt, typename... Args>
   quantity_formatter(const formatter&, OutputIt, Args...) -> quantity_formatter<OutputIt>;

src/core/include/mp-units/framework/unit.h

@@ -720,7 +720,8 @@ constexpr Out print_separator(Out out, const unit_symbol_formatting& fmt)
     if (fmt.encoding != text_encoding::unicode)
       throw std::invalid_argument(
         "'unit_symbol_separator::half_high_dot' can be only used with 'text_encoding::unicode'");
-    out = copy(std::string_view("⋅"), out).out;
+    const std::string_view dot = "⋅";
+    out = detail::copy(dot.begin(), dot.end(), out);
   } else {
     *out++ = ' ';
   }