From 92750072b0ee56116fa49f8c04835cbd89269239 Mon Sep 17 00:00:00 2001
From: Chip Hogg <chogg@aurora.tech>
Date: Thu, 7 Jul 2022 16:44:19 +0000
Subject: [PATCH] Reimplement `ratio_text()` as `magnitude_text()`

The algorithm is exactly the same; we just get our values for
`num_value`, `den_value`, and `exp10` in different ways.

The old printing logic assumed the ratio/Magnitude was an exact rational
number.  Formerly, we couldn't even _represent_ anything else, but with
Magnitude, we can.  Thus, we guard this assumption with a
`static_assert`.  Later on, we can figure out how we want to print
irrational bases and/or rational powers.  The point of this change is to
unblock us from moving to the new infrastructure.
---
 src/core/include/units/bits/unit_text.h | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/src/core/include/units/bits/unit_text.h b/src/core/include/units/bits/unit_text.h
index 49c1c3e1..736492e1 100644
--- a/src/core/include/units/bits/unit_text.h
+++ b/src/core/include/units/bits/unit_text.h
@@ -32,12 +32,19 @@ namespace units::detail {
 
 inline constexpr basic_symbol_text base_multiplier("\u00D7 10", "x 10");
 
-template<ratio R>
-constexpr auto ratio_text()
+template<Magnitude auto M>
+constexpr auto magnitude_text()
 {
-  constexpr auto num_value = R.num;
-  constexpr auto den_value = R.den;
-  constexpr auto exp10 = R.exp;
+  constexpr auto exp10 = extract_power_of_10(M);
+
+  constexpr Magnitude auto base = M / pow<exp10>(as_magnitude<10>());
+  constexpr Magnitude auto num = numerator(base);
+  constexpr Magnitude auto den = denominator(base);
+  static_assert(base == num / den, "Printing rational powers, or irrational bases, not yet supported");
+
+  constexpr auto num_value = get_value<std::intmax_t>(num);
+  constexpr auto den_value = get_value<std::intmax_t>(den);
+
 
   if constexpr (num_value == 1 && den_value == 1 && exp10 != 0) {
     return base_multiplier + superscript<exp10>();
@@ -62,6 +69,12 @@ constexpr auto ratio_text()
   }
 }
 
+template<ratio R>
+constexpr auto ratio_text()
+{
+  return magnitude_text<as_magnitude<R>()>();
+}
+
 template<Unit U, ratio R, std::size_t SymbolLen>
 constexpr auto prefix_or_ratio_text()
 {