define blade addition and subtraction

Change-Id: If09659eab51b67a15e0c2ccac795ef9c3aea9074
oliverlee · Jan 12, 2024 · b94454f · b94454f
1 parent 5499ef0
commit b94454f
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diff --git a/geometry/src/algebra.hpp b/geometry/src/algebra.hpp
@@ -171,6 +171,24 @@ struct algebra
       return blade{-x.coefficient};
     }
 
+    /// addition
+    ///
+    [[nodiscard]]
+    friend constexpr auto
+    operator+(blade x, blade y) -> blade
+    {
+      return blade{x.coefficient + y.coefficient};
+    }
+
+    /// subtraction
+    ///
+    [[nodiscard]]
+    friend constexpr auto
+    operator-(blade x, blade y) -> blade
+    {
+      return blade{x.coefficient - y.coefficient};
+    }
+
     /// scalar multiplication
     ///
     /// @{

diff --git a/test/algebra_test.cpp b/test/algebra_test.cpp
@@ -53,6 +53,12 @@ auto main() -> int
             ge(ei, 0 * ei));
       };
 
+  "blade addition"_ctest * param_ref<unit_blades> =  //
+      [](auto ei) { return expect(eq(3 * ei, ei + 2 * ei)); };
+
+  "blade subtraction"_ctest * param_ref<unit_blades> =  //
+      [](auto ei) { return expect(eq(ei, 3 * ei - 2 * ei)); };
+
   "blade uses canonical dimensions"_ctest = [] {
     return expect(
         eq(-e<1, 0>, e<0, 1>) and        //