Compilation failed on macos

[haohanyang]

Compiled with C++ 14 standard
Compiler:

Apple clang version 14.0.3 (clang-1403.0.22.14.1)
Target: x86_64-apple-darwin22.5.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

Error output

[build] /Users/haohanyang/Developer/ogs5/FEM/matrix_class.cpp:1879:16: error: explicit instantiation of 'Math_Group::vec' must occur in namespace 'Math_Group'
[build] template class vec<int>;
[build]                ^
[build] /Users/haohanyang/Developer/ogs5/FEM/matrix_class.h:440:7: note: explicit instantiation refers here
[build] class vec
[build]       ^
[build] /Users/haohanyang/Developer/ogs5/FEM/matrix_class.cpp:1880:16: error: explicit instantiation of 'Math_Group::vec' must occur in namespace 'Math_Group'
[build] template class vec<long>;
[build]                ^
[build] /Users/haohanyang/Developer/ogs5/FEM/matrix_class.h:440:7: note: explicit instantiation refers here
[build] class vec
[build]       ^
[build] /Users/haohanyang/Developer/ogs5/FEM/matrix_class.cpp:1881:16: error: explicit instantiation of 'Math_Group::vec' must occur in namespace 'Math_Group'
[build] template class vec<double>;
[build]                ^
[build] /Users/haohanyang/Developer/ogs5/FEM/matrix_class.h:440:7: note: explicit instantiation refers here
[build] class vec
[build]       ^
[build] 3 errors generated.