2 files changed, 96 insertions, 3 deletions

diff --git a/2023/flake.nix b/2023/flake.nix
index ddf0408..9971fc1 100644
--- a/2023/flake.nix
+++ b/2023/flake.nix
@@ -56,7 +56,7 @@
               #include <iostream>
               #include <fstream>
 
-              int main(void)
+              int main(int argc, char* argv[])
               {
                   int answer{};
 
@@ -81,6 +81,7 @@
 
               cat << EOF >> Makefile
               CXXFLAGS := -std=c++17
+              CPPFLAGS := -I../include
               EXE := part1 part2
 
               .PHONY: all clean configure
@@ -91,13 +92,13 @@
                 bear -- \$(MAKE) all
 
               %.o: %.cpp
-                \$(CXX) -c \$(CXXFLAGS) $< -o $@
+                \$(CXX) -c \$(CPPFLAGS) \$(CXXFLAGS) \$< -o \$@
 
               clean:
                 rm -rf \$(EXE) src/*.o compile_commands.json
 
               %: src/%.o
-                \$(CXX) $^ -o $@
+                \$(CXX) \$^ -o \$@
               EOF
             '';
           }
diff --git a/2023/include/util.h b/2023/include/util.h
new file mode 100644
index 0000000..1b5f1c5
--- /dev/null
+++ b/2023/include/util.h
@@ -0,0 +1,92 @@
+#ifndef UTIL_H
+#define UTIL_H
+
+#include <algorithm>
+#include <cstring>
+#include <stdexcept>
+#include <string>
+
+namespace util
+{
+
+/* TODO */
+constexpr char SPACE[] = " ";
+constexpr char COLON[] = ":";
+constexpr char SEMICOLON[] = ";";
+
+inline void trim(std::string& str)
+{
+    str.erase(str.begin(), std::find_if_not(str.cbegin(), str.cend(), ::isspace));
+    str.erase(std::find_if_not(str.crbegin(), str.crend(), ::isspace).base(), str.end());
+}
+
+template<const char* delim, typename Accumulate>
+void accumulate(const std::string& str, Accumulate acc)
+{
+    size_t pos{};
+    std::string elem;
+
+    while ((pos = str.find(delim)) != std::string::npos) {
+        auto sub = str.substr(0, pos);
+        trim(sub);
+        acc(sub);
+        pos += std::strlen(delim);
+    }
+}
+/* ---- */
+
+/** @brief Discard element from stream by type.
+ *
+ * @tparam T the type of the element to discard.
+ * @param stream the input stream.
+ *
+ * @return the input stream.
+ */
+template<typename T, typename CharT, typename Traits>
+std::basic_istream<CharT, Traits>& skip(std::basic_istream<CharT, Traits>& stream)
+{
+    T discard;
+    return stream >> discard;
+}
+
+/** @brief Skip token in stream.
+ *
+ * @tparam keyword the token to skip.
+ * @param stream the input stream.
+ *
+ * @return the input stream.
+ *
+ * @note The token needs to be declared as a `const char[]`, but normally,
+ * string literals are `const char*`.
+ *
+ * ```cpp
+ * constexpr char RESULT[] = "Result:";
+ *
+ * int main(int argc, char* argv[])
+ * {
+ *     int res;
+ *     std::istringstream in{ "Result: 42"}
+ *     in >> skip<RESULT> >> res;
+ *
+ *     // ...
+ *
+ *     return 0
+ * }
+ * ```
+ */
+template<const char* keyword, typename CharT, typename Traits>
+std::basic_istream<CharT, Traits>& skip(std::basic_istream<CharT, Traits>& stream)
+{
+    std::string word;
+    stream >> word;
+    if (word != keyword)
+    {
+        throw std::invalid_argument("Malformed input");
+    }
+
+    return stream;
+}
+
+} // namespace util
+
+#endif //UTIL_H