Merge pull request #368 from chiphogg/chiphogg/print-mag

Migrate remaining ratio template parameters to Magnitude

src/core/include/units/bits/basic_concepts.h

@@ -40,11 +40,11 @@ namespace units {
 // Prefix
 namespace detail {
 
-template<ratio R>
+template<Magnitude auto M>
 struct prefix_base;
 
-template<ratio R>
-void to_prefix_base(const volatile prefix_base<R>*);
+template<Magnitude auto M>
+void to_prefix_base(const volatile prefix_base<M>*);
 
 }  // namespace detail
 

src/core/include/units/bits/unit_text.h

@@ -32,24 +32,35 @@ 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()
 {
-  if constexpr (R.num == 1 && R.den == 1 && R.exp != 0) {
-    return base_multiplier + superscript<R.exp>();
-  } else if constexpr (R.num != 1 || R.den != 1 || R.exp != 0) {
-    auto txt = basic_fixed_string("[") + regular<R.num>();
-    if constexpr (R.den == 1) {
-      if constexpr (R.exp == 0) {
+  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>();
+  } else if constexpr (num_value != 1 || den_value != 1 || exp10 != 0) {
+    auto txt = basic_fixed_string("[") + regular<num_value>();
+    if constexpr (den_value == 1) {
+      if constexpr (exp10 == 0) {
         return txt + basic_fixed_string("]");
       } else {
-        return txt + " " + base_multiplier + superscript<R.exp>() + basic_fixed_string("]");
+        return txt + " " + base_multiplier + superscript<exp10>() + basic_fixed_string("]");
       }
     } else {
-      if constexpr (R.exp == 0) {
-        return txt + basic_fixed_string("/") + regular<R.den>() + basic_fixed_string("]");
+      if constexpr (exp10 == 0) {
+        return txt + basic_fixed_string("/") + regular<den_value>() + basic_fixed_string("]");
       } else {
-        return txt + basic_fixed_string("/") + regular<R.den>() + " " + base_multiplier + superscript<R.exp>() +
+        return txt + basic_fixed_string("/") + regular<den_value>() + " " + base_multiplier + superscript<exp10>() +
                basic_fixed_string("]");
       }
     }
@@ -58,22 +69,22 @@ constexpr auto ratio_text()
   }
 }
 
-template<Unit U, ratio R, std::size_t SymbolLen>
-constexpr auto prefix_or_ratio_text()
+template<Unit U, Magnitude auto M, std::size_t SymbolLen>
+constexpr auto prefix_or_magnitude_text()
 {
-  if constexpr (R.num == 1 && R.den == 1 && R.exp == 0) {
+  if constexpr (M == as_magnitude<1>()) {
     // no ratio/prefix
     return basic_fixed_string("");
   } else {
     // try to form a prefix
-    using prefix = downcast<detail::prefix_base<R>>;
+    using prefix = downcast<detail::prefix_base<M>>;
 
-    if constexpr (can_be_prefixed<U> && !is_same_v<prefix, prefix_base<R>>) {
+    if constexpr (can_be_prefixed<U> && !is_same_v<prefix, prefix_base<M>>) {
       // print as a prefixed unit
       return prefix::symbol;
     } else {
       // print as a ratio of the coherent unit
-      constexpr auto txt = ratio_text<R>();
+      constexpr auto txt = magnitude_text<M>();
       if constexpr (SymbolLen > 0 && txt.standard().size() > 0)
         return txt + basic_fixed_string(" ");
       else
@@ -147,7 +158,7 @@ constexpr auto unit_text()
     }();
 
     constexpr auto prefix_txt =
-      prefix_or_ratio_text<U, as_ratio(U::mag / coherent_unit::mag), symbol_text.standard().size()>();
+      prefix_or_magnitude_text<U, U::mag / coherent_unit::mag, symbol_text.standard().size()>();
     return prefix_txt + symbol_text;
   }
 }

src/core/include/units/magnitude.h

@@ -656,4 +656,26 @@ constexpr Magnitude auto as_magnitude()
          detail::prime_factorization_v<R.den>;
 }
 
+namespace detail {
+template<typename T, BasePower auto... BPs>
+constexpr ratio get_power(T base, magnitude<BPs...>)
+{
+  return ((BPs.get_base() == base ? BPs.power : ratio{0}) + ... + ratio{0});
+}
+
+constexpr std::intmax_t integer_part(ratio r) { return numerator(r) / denominator(r); }
+
+constexpr std::intmax_t extract_power_of_10(Magnitude auto m)
+{
+  const auto power_of_2 = get_power(2, m);
+  const auto power_of_5 = get_power(5, m);
+
+  if ((power_of_2 * power_of_5).num <= 0) {
+    return 0;
+  }
+
+  return integer_part((detail::abs(power_of_2) < detail::abs(power_of_5)) ? power_of_2 : power_of_5);
+}
+}  // namespace detail
+
 }  // namespace units

src/core/include/units/prefix.h

@@ -34,9 +34,9 @@ namespace units {
 
 namespace detail {
 
-template<ratio R>
-struct prefix_base : downcast_base<prefix_base<R>> {
-  static constexpr UNITS_MSVC_WORKAROUND(Magnitude) auto mag = as_magnitude<R>();
+template<Magnitude auto M>
+struct prefix_base : downcast_base<prefix_base<M>> {
+  static constexpr UNITS_MSVC_WORKAROUND(Magnitude) auto mag = M;
 };
 
 }  // namespace detail
@@ -54,8 +54,8 @@ struct prefix_base : downcast_base<prefix_base<R>> {
  * @tparam Symbol a text representation of the prefix
  * @tparam R factor to be used to scale a unit
  */
-template<typename Child, basic_symbol_text Symbol, ratio R>
-struct prefix : downcast_dispatch<Child, detail::prefix_base<R>, downcast_mode::on> {
+template<typename Child, basic_symbol_text Symbol, Magnitude auto M>
+struct prefix : downcast_dispatch<Child, detail::prefix_base<M>, downcast_mode::on> {
   static constexpr auto symbol = Symbol;
 };
 

src/systems/isq-iec80000/include/units/isq/iec80000/binary_prefixes.h

@@ -26,11 +26,13 @@
 
 namespace units::isq::iec80000 {
 
-struct kibi : prefix<kibi, "Ki", ratio(1'024)> {};
-struct mebi : prefix<mebi, "Mi", ratio(1'048'576)> {};
-struct gibi : prefix<gibi, "Gi", ratio(1'073'741'824)> {};
-struct tebi : prefix<tebi, "Ti", ratio(1'099'511'627'776)> {};
-struct pebi : prefix<pebi, "Pi", ratio(1'125'899'906'842'624)> {};
-struct exbi : prefix<exbi, "Ei", ratio(1'152'921'504'606'846'976)> {};
+struct kibi : prefix<kibi, "Ki", pow<10>(as_magnitude<2>())> {};
+struct mebi : prefix<mebi, "Mi", pow<20>(as_magnitude<2>())> {};
+struct gibi : prefix<gibi, "Gi", pow<30>(as_magnitude<2>())> {};
+struct tebi : prefix<tebi, "Ti", pow<40>(as_magnitude<2>())> {};
+struct pebi : prefix<pebi, "Pi", pow<50>(as_magnitude<2>())> {};
+struct exbi : prefix<exbi, "Ei", pow<60>(as_magnitude<2>())> {};
+struct zebi : prefix<zebi, "Zi", pow<70>(as_magnitude<2>())> {};
+struct yobi : prefix<yobi, "Yi", pow<80>(as_magnitude<2>())> {};
 
 }  // namespace units::isq::iec80000

src/systems/si/include/units/isq/si/prefixes.h

@@ -27,26 +27,26 @@
 namespace units::isq::si {
 
 // clang-format off
-struct yocto  : prefix<yocto, "y",             ratio(1, 1, -24)> {};
-struct zepto  : prefix<zepto, "z",             ratio(1, 1, -21)> {};
-struct atto   : prefix<atto,  "a",             ratio(1, 1, -18)> {};
-struct femto  : prefix<femto, "f",             ratio(1, 1, -15)> {};
-struct pico   : prefix<pico,  "p",             ratio(1, 1, -12)> {};
-struct nano   : prefix<nano,  "n",             ratio(1, 1,  -9)> {};
-struct micro  : prefix<micro, basic_symbol_text{"\u00b5", "u"}, ratio(1, 1,  -6)> {};
-struct milli  : prefix<milli, "m",             ratio(1, 1,  -3)> {};
-struct centi  : prefix<centi, "c",             ratio(1, 1,  -2)> {};
-struct deci   : prefix<deci,  "d",             ratio(1, 1,  -1)> {};
-struct deca   : prefix<deca,  "da",            ratio(1, 1,   1)> {};
-struct hecto  : prefix<hecto, "h",             ratio(1, 1,   2)> {};
-struct kilo   : prefix<kilo,  "k",             ratio(1, 1,   3)> {};
-struct mega   : prefix<mega,  "M",             ratio(1, 1,   6)> {};
-struct giga   : prefix<giga,  "G",             ratio(1, 1,   9)> {};
-struct tera   : prefix<tera,  "T",             ratio(1, 1,  12)> {};
-struct peta   : prefix<peta,  "P",             ratio(1, 1,  15)> {};
-struct exa    : prefix<exa,   "E",             ratio(1, 1,  18)> {};
-struct zetta  : prefix<zetta, "Z",             ratio(1, 1,  21)> {};
-struct yotta  : prefix<yotta, "Y",             ratio(1, 1,  24)> {};
+struct yocto  : prefix<yocto, "y",             pow<-24>(as_magnitude<10>())> {};
+struct zepto  : prefix<zepto, "z",             pow<-21>(as_magnitude<10>())> {};
+struct atto   : prefix<atto,  "a",             pow<-18>(as_magnitude<10>())> {};
+struct femto  : prefix<femto, "f",             pow<-15>(as_magnitude<10>())> {};
+struct pico   : prefix<pico,  "p",             pow<-12>(as_magnitude<10>())> {};
+struct nano   : prefix<nano,  "n",             pow<-9>(as_magnitude<10>())> {};
+struct micro  : prefix<micro, basic_symbol_text{"\u00b5", "u"}, pow<-6>(as_magnitude<10>())> {};
+struct milli  : prefix<milli, "m",             pow<-3>(as_magnitude<10>())> {};
+struct centi  : prefix<centi, "c",             pow<-2>(as_magnitude<10>())> {};
+struct deci   : prefix<deci,  "d",             pow<-1>(as_magnitude<10>())> {};
+struct deca   : prefix<deca,  "da",            pow<1>(as_magnitude<10>())> {};
+struct hecto  : prefix<hecto, "h",             pow<2>(as_magnitude<10>())> {};
+struct kilo   : prefix<kilo,  "k",             pow<3>(as_magnitude<10>())> {};
+struct mega   : prefix<mega,  "M",             pow<6>(as_magnitude<10>())> {};
+struct giga   : prefix<giga,  "G",             pow<9>(as_magnitude<10>())> {};
+struct tera   : prefix<tera,  "T",             pow<12>(as_magnitude<10>())> {};
+struct peta   : prefix<peta,  "P",             pow<15>(as_magnitude<10>())> {};
+struct exa    : prefix<exa,   "E",             pow<18>(as_magnitude<10>())> {};
+struct zetta  : prefix<zetta, "Z",             pow<21>(as_magnitude<10>())> {};
+struct yotta  : prefix<yotta, "Y",             pow<24>(as_magnitude<10>())> {};
 // clang-format on
 
 }  // namespace units::isq::si

test/unit_test/runtime/magnitude_test.cpp

@@ -610,4 +610,30 @@ TEST_CASE("strictly_increasing")
   }
 }
 
+TEST_CASE("extract_power_of_10")
+{
+  SECTION("Picks out positive powers")
+  {
+    CHECK(extract_power_of_10(as_magnitude<10>()) == 1);
+    CHECK(extract_power_of_10(as_magnitude<20>()) == 1);
+    CHECK(extract_power_of_10(as_magnitude<40>()) == 1);
+    CHECK(extract_power_of_10(as_magnitude<50>()) == 1);
+    CHECK(extract_power_of_10(as_magnitude<100>()) == 2);
+  }
+
+  SECTION("Picks out negative powers")
+  {
+    constexpr auto ONE = as_magnitude<1>();
+    CHECK(extract_power_of_10(ONE / as_magnitude<10>()) == -1);
+    CHECK(extract_power_of_10(ONE / as_magnitude<20>()) == -1);
+    CHECK(extract_power_of_10(ONE / as_magnitude<40>()) == -1);
+    CHECK(extract_power_of_10(ONE / as_magnitude<50>()) == -1);
+    CHECK(extract_power_of_10(ONE / as_magnitude<100>()) == -2);
+  }
+
+  SECTION("Zero if signs disagree") { CHECK(extract_power_of_10(as_magnitude<2>() / as_magnitude<5>()) == 0); }
+
+  SECTION("Handles rational powers") { CHECK(extract_power_of_10(sqrt(as_magnitude<1000>())) == 1); }
+}
+
 }  // namespace