use multiplicities class; fix cmakelists typo

cosets/CMakeLists.txt

@@ -13,6 +13,6 @@ add_custom_command(
         ${CMAKE_CURRENT_BINARY_DIR}/shaders
 )
 
-add_executable(coxeter scr/coxeter.cpp)
+add_executable(coxeter src/coxeter.cpp)
 add_executable(mirror src/mirrors.cpp)
 target_link_libraries(mirror PRIVATE glm)

cosets/src/mirrors.cpp

@@ -1,11 +1,10 @@
 #include "util/mirrors.hpp"
 
 int main(int argc, char *argv[]) {
-   auto normals = mirror<3>({
-      {},
-      {4},
-      {2, 3}
-   });
+   auto normals = mirror<3>(Multiplicites<3>({
+      {0, 1, 4},
+      {1, 2, 3}
+   }));
 
    for (const auto &normal : normals) {
       std::cout << glm::to_string(normal) << std::endl;

cosets/src/util/coxeter.hpp

@@ -4,6 +4,38 @@
 #include <algorithm>
 #include <cmath>
 
+struct Mult {
+   int a, b, mult;
+};
+
+template<int N>
+struct Multiplicites {
+   std::vector<int> mults;
+
+   explicit Multiplicites(std::vector<Mult> vals) {
+      mults = std::vector<int>(N * (N - 1) / 2, 2);
+      for (const auto &mult : vals) {
+         set(mult.a, mult.b, mult.mult);
+      }
+   }
+
+   void set(int a, int b, int mult) {
+      if (a > N or b > N) throw std::logic_error("mirror does not exist");
+      if (a == b) throw std::logic_error("cannot compare mirror to itself");
+      if (a < b) std::swap(a, b); // a is bigger
+
+      mults[a + b] = mult;
+   }
+
+   int get(int a, int b) const {
+      if (a > N or b > N) throw std::logic_error("mirror does not exist");
+      if (a == b) throw std::logic_error("cannot compare mirror to itself");
+      if (a < b) std::swap(a, b); // a is bigger
+
+      return mults[a + b];
+   }
+};
+
 
 struct Table {
    int N;

cosets/src/util/mirrors.hpp

@@ -6,9 +6,10 @@
 #include <iomanip>
 
 #include "numeric.hpp"
+#include "coxeter.hpp"
 
 template<int N>
-std::vector<glm::vec4> mirror(const float (&arr)[N][N]) {
+std::vector<glm::vec4> mirror(const Multiplicites<N> &mults) {
    static_assert(1 <= N and N <= 4, "Vector size is unsupported");
 
    std::vector<glm::vec4> mirrors{};
@@ -16,7 +17,7 @@ std::vector<glm::vec4> mirror(const float (&arr)[N][N]) {
       glm::vec4 vp{};
       for (int m = 0; m < p; ++m) {
          glm::vec4 vq = mirrors[m];
-         vp[m] = (cos(M_PI / arr[p][m]) - dot(m, vp, vq)) / vq[m];
+         vp[m] = (cos(M_PI / mults.get(p, m)) - dot(m, vp, vq)) / vq[m];
       }
       vp[p] = std::sqrt(1 - glm::dot(vp, vp));