Resolve "clang compiler error for VerticalFFAMagnet"

src/Classic/AbsBeamline/VerticalFFAMagnet.cpp

@@ -12,6 +12,8 @@
 
 #include "AbsBeamline/VerticalFFAMagnet.h"
 
+#include <cmath>
+
 VerticalFFAMagnet::VerticalFFAMagnet(const std::string &name)
         : Component(name), straightGeometry_m(1.) {
     setElType(isDrift);
@@ -79,7 +81,7 @@ void VerticalFFAMagnet::accept(BeamlineVisitor& visitor) const {
 
 
 bool VerticalFFAMagnet::getFieldValue(const Vector_t &R, Vector_t &B) const {
-    if (abs(R[0]) > halfWidth_m ||
+    if (std::abs(R[0]) > halfWidth_m ||
         R[2] < 0. || R[2] > bbLength_m ||
         R[1] < -zNegExtent_m || R[1] > zPosExtent_m) {
         return true;

tests/classic_src/AbsBeamline/VerticalFFAMagnetTest.cpp

@@ -132,7 +132,7 @@ TEST_F(VerticalFFAMagnetTest, MaxwellTest) {
         //maxTest.printLine(std::cerr, pos, 0.);
         double div = maxTest.divB(pos, 0.);
         double curl = euclidean_norm(maxTest.curlB(pos, 0.));
-        EXPECT_LT(abs(div), abs(divOld)) << i;
+        EXPECT_LT(std::abs(div), std::abs(divOld)) << i;
         EXPECT_LT(curl, 1e-11);
         std::cerr << "Max Order: " << i << " |curlB|: " << curl
                   << " DivB: " << div << std::endl;