Small refactoring of new ratio (resolves #14)

README.md

@@ -202,6 +202,7 @@ NOTE: This library as of now compiles correctly only with gcc-9.1 and newer.
   - Added official CGS system support
   - Added official data information system support
   - Repository file tree cleanup
+  - `ratio` refactored to contain `Exp` template parameter
 
 - 0.4.0 Nov 17, 2019
   - Support for derived dimensions in `exp` added

doc/DESIGN.md

@@ -74,7 +74,16 @@ struct scaled_unit : downcast_base<scaled_unit<R, U>> {
 };
 ```
 
-The above type is a framework's private type and the user should never instantiate it directly.
+where:
+
+```cpp
+template<typename R>
+concept UnitRatio = Ratio<R> && (R::num * R::den > 0);
+```
+
+and `Ratio` is satisfied by any instantiation of `units::ratio<Num, Den, Exp>`.
+
+The `scaled_unit` type is a framework's private type and the user should never instantiate it directly.
 The public user interface to create units consists of:
 
 ![Units UML](units.png)
@@ -143,8 +152,8 @@ namespace units::si {
 
 // prefixes
 struct prefix : prefix_type {};
-struct centi : units::prefix<kilo, prefix, "c", ratio<1, 100>> {};
-struct kilo : units::prefix<kilo, prefix, "k", ratio<1'000>> {};
+struct centi : units::prefix<centi, prefix, "c", ratio<1, 1, -2>> {};
+struct kilo : units::prefix<kilo, prefix, "k", ratio<1, 1, 3>> {};
 
 // length
 struct metre : named_unit<metre, "m", prefix> {};

src/include/units/bits/unit_text.h

@@ -31,12 +31,14 @@ constexpr auto ratio_text()
 {
   if constexpr(Ratio::num != 1 || Ratio::den != 1 || Ratio::exp != 0) {
     auto txt = basic_fixed_string("[") + regular<Ratio::num>();
-    if constexpr(Ratio::den == 1 && Ratio::exp == 0) {
-      return txt + basic_fixed_string("]");
-    }
-    else if constexpr (Ratio::den == 1) {
-      return txt + basic_fixed_string(" \u00D7 10") + superscript<Ratio::exp>() +
-          basic_fixed_string("]");
+    if constexpr(Ratio::den == 1) {
+      if constexpr(Ratio::exp == 0) {
+        return txt + basic_fixed_string("]");
+      }
+      else {
+        return txt + basic_fixed_string(" \u00D7 10") + superscript<Ratio::exp>() +
+            basic_fixed_string("]");
+      }
     }
     else {
       return txt + basic_fixed_string("/") + regular<Ratio::den>() +

src/include/units/data/prefixes.h

@@ -23,7 +23,6 @@
 #pragma once
 
 #include <units/prefix.h>
-#include <ratio>
 
 namespace units::data {
 

src/include/units/ratio.h

@@ -40,7 +40,8 @@ template<typename T>
   return v < 0 ? -v : v;
 }
 
-constexpr std::tuple<std::intmax_t, std::intmax_t, std::intmax_t>  normalize(std::intmax_t num, std::intmax_t den, std::intmax_t exp) {
+constexpr std::tuple<std::intmax_t, std::intmax_t, std::intmax_t>  normalize(std::intmax_t num, std::intmax_t den, std::intmax_t exp)
+{
   std::intmax_t gcd = std::gcd(num, den);
   num = num * (den < 0 ? -1 : 1) / gcd;
   den = detail::abs(den) / gcd;

test/unit_test/runtime/fmt_test.cpp

@@ -296,7 +296,7 @@ TEST_CASE("operator<< on a quantity", "[text][ostream][fmt]")
 
       SECTION("iostream")
       {
-        CHECK(stream.str() == "8 [1 \u00D7 10⁻²]m³");
+        CHECK(stream.str() == "8 [1 × 10⁻²]m³");
       }
 
       SECTION("fmt with default format {} on a quantity")
@@ -317,7 +317,7 @@ TEST_CASE("operator<< on a quantity", "[text][ostream][fmt]")
 
       SECTION("iostream")
       {
-        CHECK(stream.str() == "2 [6 \u00D7 10¹]Hz");
+        CHECK(stream.str() == "2 [6 × 10¹]Hz");
       }
 
       SECTION("fmt with default format {} on a quantity")
@@ -338,7 +338,7 @@ TEST_CASE("operator<< on a quantity", "[text][ostream][fmt]")
 
       SECTION("iostream")
       {
-        CHECK(stream.str() == "10 [1/6 \u00D7 10⁻¹]W");
+        CHECK(stream.str() == "10 [1/6 × 10⁻¹]W");
       }
 
       SECTION("fmt with default format {} on a quantity")
@@ -359,7 +359,7 @@ TEST_CASE("operator<< on a quantity", "[text][ostream][fmt]")
 
       SECTION("iostream")
       {
-        CHECK(stream.str() == "30 [1/6 \u00D7 10²]W");
+        CHECK(stream.str() == "30 [1/6 × 10²]W");
       }
 
       SECTION("fmt with default format {} on a quantity")
@@ -404,7 +404,7 @@ TEST_CASE("operator<< on a quantity", "[text][ostream][fmt]")
 
       SECTION("iostream")
       {
-        CHECK(stream.str() == "8 [1 \u00D7 10³]m⋅s");
+        CHECK(stream.str() == "8 [1 × 10³]m⋅s");
       }
 
       SECTION("fmt with default format {} on a quantity")
@@ -425,7 +425,7 @@ TEST_CASE("operator<< on a quantity", "[text][ostream][fmt]")
 
       SECTION("iostream")
       {
-        CHECK(stream.str() == "2 [6 \u00D7 10¹]kg/s");
+        CHECK(stream.str() == "2 [6 × 10¹]kg/s");
       }
 
       SECTION("fmt with default format {} on a quantity")
@@ -446,7 +446,7 @@ TEST_CASE("operator<< on a quantity", "[text][ostream][fmt]")
 
       SECTION("iostream")
       {
-        CHECK(stream.str() == "10 [1/6 \u00D7 10⁻¹]kg/s");
+        CHECK(stream.str() == "10 [1/6 × 10⁻¹]kg/s");
       }
 
       SECTION("fmt with default format {} on a quantity")
@@ -467,7 +467,7 @@ TEST_CASE("operator<< on a quantity", "[text][ostream][fmt]")
 
       SECTION("iostream")
       {
-        CHECK(stream.str() == "30 [6 \u00D7 10⁻²]1/m⋅s");
+        CHECK(stream.str() == "30 [6 × 10⁻²]1/m⋅s");
       }
 
       SECTION("fmt with default format {} on a quantity")