foo.cc: In function 'std::string bigIntToStr(BigInt)':
foo.cc:26:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   26 |     for (int i = 0; i < num.size(); i++) {
      |                     ~~^~~~~~~~~~~~
foo.cc: In function 'BigInt add(BigInt, BigInt)':
foo.cc:39:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |     for (int i = 0; i < a.size() || i < b.size(); i++) {
      |                     ~~^~~~~~~~~~
foo.cc:39:39: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   39 |     for (int i = 0; i < a.size() || i < b.size(); i++) {
      |                                     ~~^~~~~~~~~~
foo.cc:41:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   41 |         if (i < a.size()) tmp += a[i];
      |             ~~^~~~~~~~~~
foo.cc:42:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 |         if (i < b.size()) tmp += b[i];
      |             ~~^~~~~~~~~~
foo.cc: In function 'BigInt sub(BigInt, BigInt)':
foo.cc:53:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   53 |     for (int i = 0; i < a.size() || i < b.size(); i++) {
      |                     ~~^~~~~~~~~~
foo.cc:53:39: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   53 |     for (int i = 0; i < a.size() || i < b.size(); i++) {
      |                                     ~~^~~~~~~~~~
foo.cc:55:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   55 |         if (i < a.size()) tmp += a[i];
      |             ~~^~~~~~~~~~
foo.cc:56:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   56 |         if (i < b.size()) tmp -= b[i];
      |             ~~^~~~~~~~~~
foo.cc: In function 'BigInt mul(BigInt, int)':
foo.cc:72:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   72 |     for (int i = 0; i < a.size(); i++) {
      |                     ~~^~~~~~~~~~
foo.cc: In function 'BigInt mul(BigInt, BigInt)':
foo.cc:83:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   83 |     for (int i = 0; i < a.size(); i++) {
      |                     ~~^~~~~~~~~~
foo.cc:85:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   85 |         for (int j = 0; j < b.size(); j++) {
      |                         ~~^~~~~~~~~~
foo.cc: In function 'BigInt div(BigInt, BigInt, BigInt&)':
foo.cc:123:16: error: reference to 'less' is ambiguous
  123 |         while (less(b, r)) {
      |                ^~~~
In file included from /nix/store/wy4ywjsch9q2hj5lphqjdg9p2kf7w0ls-gcc-11.3.0/include/c++/11.3.0/string:48,
                 from /nix/store/wy4ywjsch9q2hj5lphqjdg9p2kf7w0ls-gcc-11.3.0/include/c++/11.3.0/bits/locale_classes.h:40,
                 from /nix/store/wy4ywjsch9q2hj5lphqjdg9p2kf7w0ls-gcc-11.3.0/include/c++/11.3.0/bits/ios_base.h:41,
                 from /nix/store/wy4ywjsch9q2hj5lphqjdg9p2kf7w0ls-gcc-11.3.0/include/c++/11.3.0/ios:42,
                 from /nix/store/wy4ywjsch9q2hj5lphqjdg9p2kf7w0ls-gcc-11.3.0/include/c++/11.3.0/ostream:38,
                 from /nix/store/wy4ywjsch9q2hj5lphqjdg9p2kf7w0ls-gcc-11.3.0/include/c++/11.3.0/iostream:39,
                 from foo.cc:1:
/nix/store/wy4ywjsch9q2hj5lphqjdg9p2kf7w0ls-gcc-11.3.0/include/c++/11.3.0/bits/stl_function.h:395:12: note: candidates are: 'template<class _Tp> struct std::less'
  395 |     struct less : public binary_function<_Tp, _Tp, bool>
      |            ^~~~
foo.cc:96:6: note:                 'bool less(BigInt, BigInt)'
   96 | bool less(BigInt a, BigInt b) {
      |      ^~~~

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