avoid using <numbers> for getting pi

include/common.h

@@ -3,7 +3,7 @@
 #include <filesystem>
 #include <functional>
 #include <memory>
-#include <numbers>
+#include <cmath>
 #include <numeric>
 #include <fstream>
 #include <sstream>
@@ -25,6 +25,8 @@
 #include "random.h"
 
 namespace globals {
+    extern const float pi;
+
     // Given as command line arguments
     extern std::string input_file;
     extern std::string output_ext;

src/cmd/filter.cpp

@@ -120,7 +120,7 @@ std::shared_ptr<cyHairFile> cmd::exec::filter(std::shared_ptr<cyHairFile> hairfi
                 const float s = (la + lb + lc) / 2.0f;
                 const float A = std::sqrt(s * (s - la) * (s - lb) * (s - lc));
                 const float circumradius_reciprocal = A > 0.0f ? 1.0f / (la * lb * lc / (4.0f * A)) : 0.0f;
-                const float turning_angle = 180.0f - std::acos(std::clamp((la * la + lb * lb - lc * lc) / (2.0f * la * lb), -1.0f, 1.0f)) * 180.0f / std::numbers::pi_v<float>;
+                const float turning_angle = 180.0f - std::acos(std::clamp((la * la + lb * lb - lc * lc) / (2.0f * la * lb), -1.0f, 1.0f)) * 180.0f / globals::pi;
 
                 max_point_circumradius_reciprocal = std::max(max_point_circumradius_reciprocal, circumradius_reciprocal);
                 min_point_circumradius_reciprocal = std::min(min_point_circumradius_reciprocal, circumradius_reciprocal);

src/cmd/getcurvature.cpp

@@ -79,7 +79,7 @@ std::shared_ptr<cyHairFile> cmd::exec::getcurvature(std::shared_ptr<cyHairFile>
         const VectorXf tangent_cross_norm = tangent_cross.rowwise().norm();
         const VectorXf turning_angle = tangent_cross_norm.array().asin();
 
-        const VectorXi is_straight = (turning_angle.array() < ::param.angle_threshold * std::numbers::pi / 180.0).cast<int>();
+        const VectorXi is_straight = (turning_angle.array() < ::param.angle_threshold * globals::pi / 180.0).cast<int>();
 
         // If the strand is completely straight, simply set binormal to a random vector
         if (is_straight.sum() == nsegs[i]-1) {

src/cmd/stats.cpp

@@ -114,7 +114,7 @@ std::shared_ptr<cyHairFile> cmd::exec::stats(std::shared_ptr<cyHairFile> hairfil
                 const float s = (la + lb + lc) / 2.0f;
                 const float A = std::sqrt(s * (s - la) * (s - lb) * (s - lc));
                 const float circumradius_reciprocal = A > 0.0f ? 1.0f / (la * lb * lc / (4.0f * A)) : 0.0f;
-                const float turning_angle = 180.0f - std::acos(std::clamp((la * la + lb * lb - lc * lc) / (2.0f * la * lb), -1.0f, 1.0f)) * 180.0f / std::numbers::pi_v<float>;
+                const float turning_angle = 180.0f - std::acos(std::clamp((la * la + lb * lb - lc * lc) / (2.0f * la * lb), -1.0f, 1.0f)) * 180.0f / globals::pi;
 
                 PointInfo point_info;
                 point_info.idx = offset + j + 1;

src/globals.cpp

@@ -2,6 +2,8 @@
 #include "io.h"
 
 namespace globals {
+    const float pi = std::acos(-1.0f);
+
     // Given as command line arguments
     std::string input_file;
     std::string output_ext;