From dba8b07eb5de1a466152161c0458e53a906fcd9e Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Thu, 3 Oct 2024 19:34:16 +0200
Subject: [PATCH] feat: added support for printing powers of magnitude
 constants

---
 src/core/include/mp-units/bits/text_tools.h     |  2 ++
 src/core/include/mp-units/framework/magnitude.h | 14 ++++++++------
 test/static/unit_symbol_test.cpp                |  4 ++++
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/src/core/include/mp-units/bits/text_tools.h b/src/core/include/mp-units/bits/text_tools.h
index 0b1fa7f71..46e5fa9c5 100644
--- a/src/core/include/mp-units/bits/text_tools.h
+++ b/src/core/include/mp-units/bits/text_tools.h
@@ -146,6 +146,8 @@ constexpr Out copy_symbol_exponent(text_encoding encoding, bool negative_power,
     }
     constexpr auto txt = superscript<r.num>();
     return copy<CharT>(txt, encoding, out);
+  } else {
+    return out;
   }
 }
 
diff --git a/src/core/include/mp-units/framework/magnitude.h b/src/core/include/mp-units/framework/magnitude.h
index a05354b85..c52074e8b 100644
--- a/src/core/include/mp-units/framework/magnitude.h
+++ b/src/core/include/mp-units/framework/magnitude.h
@@ -353,9 +353,12 @@ template<typename CharT, std::output_iterator<CharT> Out, auto M, auto... Rest>
 [[nodiscard]] consteval auto mag_constants_text(Out out, magnitude<M, Rest...>, const unit_symbol_formatting& fmt,
                                                 bool negative_power)
 {
-  return ((out = copy_symbol<CharT>(get_base(M).symbol, fmt.encoding, negative_power, out)), ...,
-          (print_separator<CharT>(out, fmt),
-           out = copy_symbol<CharT>(get_base(Rest).symbol, fmt.encoding, negative_power, out)));
+  auto to_symbol = [&]<typename T>(T v) {
+    out = copy_symbol<CharT>(get_base(v).symbol, fmt.encoding, negative_power, out);
+    constexpr ratio r = get_exponent(T{});
+    return copy_symbol_exponent<CharT, abs(r.num), r.den>(fmt.encoding, negative_power, out);
+  };
+  return (to_symbol(M), ..., (print_separator<CharT>(out, fmt), to_symbol(Rest)));
 }
 
 template<typename CharT, Magnitude auto Num, Magnitude auto Den, Magnitude auto NumConstants,
@@ -501,7 +504,6 @@ struct magnitude : detail::magnitude_base<magnitude<Ms...>> {
 
   [[nodiscard]] friend consteval auto _denominator(magnitude) { return _numerator(pow<-1>(magnitude{})); }
 
-
   [[nodiscard]] friend consteval auto _remove_positive_powers(magnitude)
   {
     return (magnitude<>{} * ... * detail::remove_positive_power(magnitude<Ms>{}));
@@ -717,8 +719,8 @@ constexpr Magnitude auto mag_ratio = detail::prime_factorization_v<N> / detail::
 /**
  * @brief  Create a Magnitude which is some rational number raised to a rational power.
  */
-template<std::intmax_t Base, int Num, int Den = 1>
-  requires detail::gt_zero<Base>
+template<MagArg auto Base, int Num, int Den = 1>
+  requires detail::gt_zero<detail::get_base_value(Base)>
 constexpr Magnitude auto mag_power = pow<Num, Den>(mag<Base>);
 
 /**
diff --git a/test/static/unit_symbol_test.cpp b/test/static/unit_symbol_test.cpp
index 648503272..bca0d25da 100644
--- a/test/static/unit_symbol_test.cpp
+++ b/test/static/unit_symbol_test.cpp
@@ -168,6 +168,10 @@ static_assert(unit_symbol<usf{.encoding = ascii, .solidus = always}>(mag_ratio<1
               "[1/(2 pi) m]");
 static_assert(unit_symbol(mag_ratio<1, 2> * mag<pi> * metre) == "[𝜋/2 m]");
 
+static_assert(unit_symbol(mag_power<pi, 2> * one) == "[𝜋²]");
+static_assert(unit_symbol<usf{.encoding = ascii}>(mag_power<pi, 2> * one) == "[pi^2]");
+static_assert(unit_symbol(mag_power<pi, 1, 2> * metre) == "[𝜋^(1/2) m]");
+static_assert(unit_symbol<usf{.encoding = ascii}>(mag_power<pi, 1, 2> * metre) == "[pi^(1/2) m]");
 
 static_assert(unit_symbol(mag<pi> * mag<e> * one) == "[e 𝜋]");
 static_assert(unit_symbol(mag<e> * mag<pi> * one) == "[e 𝜋]");