feat(example): add print_hex example

examples/CMakeLists.txt

@@ -1,5 +1,9 @@
 add_custom_target(examples)
 
+add_executable(example_print_hex print_hex.cpp)
+target_link_libraries(example_print_hex PRIVATE errors)
+add_dependencies(examples example_print_hex)
+
 add_executable(example_read_file read_file.cpp)
 target_link_libraries(example_read_file PRIVATE errors errors_format)
 add_dependencies(examples example_read_file)

examples/print_hex.cpp

@@ -0,0 +1,27 @@
+#include <errors/error.hpp>
+#include <iostream>
+
+errors::Error print_hex(const char* number_str) {
+  int number = std::atoi(number_str);
+  if (number == 0) {
+    return errors::make("is not a number");
+  }
+
+  std::cout << std::hex << number << std::endl;
+  return errors::nil();
+}
+
+int main(int argc, char **argv) {
+  if (argc < 2) {
+    std::cerr << "usage: " << argv[0] << " <number>" << std::endl;
+    return 1;
+  }
+
+  const auto err = print_hex(argv[1]);
+  if (err) {
+    std::cerr << err << std::endl;
+    return 1;
+  }
+
+  return 0;
+}