diff --git a/include/argparse.hpp b/include/argparse.hpp
index f372dd3..067d490 100644
--- a/include/argparse.hpp
+++ b/include/argparse.hpp
@@ -73,12 +73,6 @@ using enable_if_container = std::enable_if_t<is_container_v<T>, T>;
 
 template <typename T>
 using enable_if_not_container = std::enable_if_t<!is_container_v<T>, T>;
-
-// Check if string (haystack) starts with a substring (needle)
-bool starts_with(const std::string& haystack, const std::string& needle) {
-  return needle.length() <= haystack.length()
-    && std::equal(needle.begin(), needle.end(), haystack.begin());
-}
 }
 
 class Argument {
@@ -118,6 +112,33 @@ public:
     return *this;
   }
 
+  template <typename Iterator>
+  Iterator consume(Iterator start, Iterator end, std::string usedName = {}) {
+    if (mIsUsed) {
+      throw std::runtime_error("Duplicate argument");
+    }
+    mIsUsed = true;
+    mUsedName = std::move(usedName);
+    if (mNumArgs == 0) {
+      mValues.emplace_back(mImplicitValue);
+      return start;
+    }
+    else if (mNumArgs <= std::distance(start, end)) {
+      end = std::next(start, mNumArgs);
+      if (std::any_of(start, end, Argument::is_optional)) {
+          throw std::runtime_error("optional argument in parameter sequence");
+      }
+      std::transform(start, end, std::back_inserter(mValues), mAction);
+      return end;
+    }
+    else if (mDefaultValue.has_value()) {
+      return start;
+    }
+    else {
+      throw std::runtime_error("Too few arguments");
+    }
+  }
+
   /*
    * @throws std::runtime_error if argument values are not valid
    */
@@ -134,7 +155,7 @@ public:
       }
     }
     else {
-      if (mValues.size() != mNumArgs) {
+      if (mValues.size() != mNumArgs && !mDefaultValue.has_value()) {
         std::stringstream stream;
         stream << "error: " << mUsedName << ": expected " << mNumArgs << " argument(s). "
                << mValues.size() << " provided.\n" << std::endl;
@@ -180,7 +201,11 @@ public:
   private:
     // If an argument starts with "-" or "--", then it's optional
     static bool is_optional(const std::string& aName) {
-      return (starts_with(aName, "--") || starts_with(aName, "-"));
+      return (!aName.empty() && aName[0] == '-');
+    }
+
+    static bool is_positional(const std::string& aName) {
+      return !is_optional(aName);
     }
 
     /*
@@ -302,8 +327,9 @@ class ArgumentParser {
      * @throws std::runtime_error in case of any invalid argument
      */
     void parse_args(int argc, const char * const argv[]) {
-      parse_args_internal(argc, argv);
-      parse_args_validate();
+      std::vector<std::string> arguments;
+      std::copy(argv, argv + argc, std::back_inserter(arguments));
+      parse_args(arguments);
     }
 
     /* Getter enabled for all template types other than std::vector and std::list
@@ -406,132 +432,45 @@ class ArgumentParser {
      * @throws std::runtime_error in case of any invalid argument
      */
     void parse_args_internal(const std::vector<std::string>& aArguments) {
-      std::vector<char*> argv;
-      for (const auto& arg : aArguments)
-        argv.emplace_back(const_cast<char*>(arg.data()));
-      argv.emplace_back(nullptr);
-      return parse_args_internal(int(argv.size()) - 1, argv.data());
-    }
-
-    /*
-     * @throws std::runtime_error in case of any invalid argument
-     */
-    void parse_args_internal(int argc, const char * const argv[]) {
-      if (mProgramName.empty() && argc > 0)
-        mProgramName = argv[0];
-      for (int i = 1; i < argc; i++) {
-        auto tCurrentArgument = std::string(argv[i]);
+      if (mProgramName.empty() && !aArguments.empty()) {
+        mProgramName = aArguments.front();
+      }
+      auto end = std::end(aArguments);
+      auto positionalArgumentIt = std::begin(mPositionalArguments);
+      for (auto it = std::next(std::begin(aArguments)); it != end;) {
+        const auto& tCurrentArgument = *it;
         if (tCurrentArgument == Argument::mHelpOption || tCurrentArgument == Argument::mHelpOptionLong) {
           throw std::runtime_error("help called");
         }
-        auto tIterator = mArgumentMap.find(argv[i]);
-        if (tIterator != mArgumentMap.end()) {
-          // Start parsing optional argument
-          auto tArgument = tIterator->second;
-          tArgument->mUsedName = tCurrentArgument;
-          tArgument->mIsUsed = true;
-          auto tCount = tArgument->mNumArgs;
-
-          // Check to see if implicit value should be used
-          // Two cases to handle here:
-          // (1) User has explicitly programmed nargs to be 0
-          // (2) User has provided an implicit value, which also sets nargs to 0
-          if (tCount == 0) {
-            // Use implicit value for this optional argument
-            tArgument->mValues.emplace_back(tArgument->mImplicitValue);
-            tArgument->mRawValues.emplace_back();
-            tCount = 0;
+        if (Argument::is_positional(tCurrentArgument)) {
+          if (positionalArgumentIt == std::end(mPositionalArguments)) {
+            throw std::runtime_error("Maximum number of positional arguments exceeded");
           }
-          while (tCount > 0) {
-            i = i + 1;
-            if (i < argc) {
-              tArgument->mUsedName = tCurrentArgument;
-              tArgument->mRawValues.emplace_back(argv[i]);
-              if (tArgument->mAction != nullptr)
-                tArgument->mValues.emplace_back(tArgument->mAction(argv[i]));
-              else {
-                if (tArgument->mDefaultValue.has_value())
-                  tArgument->mValues.emplace_back(tArgument->mDefaultValue);
-                else
-                  tArgument->mValues.emplace_back(std::string(argv[i]));
-              }
+          auto tArgument = *(positionalArgumentIt++);
+          it = tArgument->consume(it, end);
+        }
+        else if (auto tIterator = mArgumentMap.find(tCurrentArgument); tIterator != mArgumentMap.end()) {
+            auto tArgument = tIterator->second;
+            it = tArgument->consume(std::next(it), end, tCurrentArgument);
+        }
+        else if (const auto& tCompoundArgument = tCurrentArgument;
+                 tCompoundArgument.size() > 1 &&
+                 tCompoundArgument[0] == '-'  &&
+                 tCompoundArgument[1] != '-') {
+          ++it;
+          for (size_t j = 1; j < tCompoundArgument.size(); j++) {
+            auto tCurrentArgument = std::string{'-', tCompoundArgument[j]};
+            if (auto tIterator = mArgumentMap.find(tCurrentArgument); tIterator != mArgumentMap.end()) {
+              auto tArgument = tIterator->second;
+              it = tArgument->consume(it, end, tCurrentArgument);
+            }
+            else {
+              throw std::runtime_error("Unknown argument");
             }
-            tCount -= 1;
           }
         }
         else {
-          if (Argument::is_optional(argv[i])) {
-            // This is possibly a compound optional argument
-            // Example: We have three optional arguments -a, -u and -x
-            // The user provides ./main -aux ...
-            // Here -aux is a compound optional argument
-            std::string tCompoundArgument = std::string(argv[i]);
-            if (tCompoundArgument.size() > 1 && tCompoundArgument[0] == '-' && tCompoundArgument[1] != '-') {
-              for (size_t j = 1; j < tCompoundArgument.size(); j++) {
-                std::string tArgument(1, tCompoundArgument[j]);
-                size_t tNumArgs = 0;
-                tIterator = mArgumentMap.find("-" + tArgument);
-                if (tIterator != mArgumentMap.end()) {
-                  auto tArgumentObject = tIterator->second;
-                  tNumArgs = tArgumentObject->mNumArgs;
-                  std::vector<std::string> tArgumentsForRecursiveParsing = {"", "-" + tArgument};
-                  while (tNumArgs > 0 && i < argc) {
-                    i += 1;
-                    if (i < argc) {
-                      tArgumentsForRecursiveParsing.emplace_back(argv[i]);
-                      tNumArgs -= 1;
-                    }
-                  }
-                  parse_args_internal(tArgumentsForRecursiveParsing);
-                }
-                else {
-                  if (!tArgument.empty() && tArgument[0] == '-')
-                    std::cout << "warning: unrecognized optional argument " << tArgument
-                              << std::endl;
-                  else
-                    std::cout << "warning: unrecognized optional argument -" << tArgument
-                              << std::endl;
-                }
-              }
-            }
-            else {
-              std::cout << "warning: unrecognized optional argument " << tCompoundArgument << std::endl;
-            }
-          }
-          else {
-            // This is a positional argument.
-            // Parse and save into mPositionalArguments vector
-            if (mNextPositionalArgument >= mPositionalArguments.size()) {
-              std::stringstream stream;
-              stream << "error: unexpected positional argument " << argv[i] << std::endl;
-              throw std::runtime_error(stream.str());
-            }
-            auto tArgument = mPositionalArguments[mNextPositionalArgument];
-            auto tCount = tArgument->mNumArgs - tArgument->mRawValues.size();
-            while (tCount > 0) {
-              tIterator = mArgumentMap.find(argv[i]);
-              if (tIterator != mArgumentMap.end() || Argument::is_optional(argv[i])) {
-                i = i - 1;
-                break;
-              }
-              if (i < argc) {
-                tArgument->mUsedName = tCurrentArgument;
-                tArgument->mRawValues.emplace_back(argv[i]);
-                if (tArgument->mAction != nullptr)
-                  tArgument->mValues.emplace_back(tArgument->mAction(argv[i]));
-                else {
-                  if (tArgument->mDefaultValue.has_value())
-                    tArgument->mValues.emplace_back(tArgument->mDefaultValue);
-                  else
-                    tArgument->mValues.emplace_back(std::string(argv[i]));
-                }
-              }
-              tCount -= 1;
-              if (tCount > 0) i += 1;
-            }
-            if (tCount == 0)
-              mNextPositionalArgument += 1;
-          }
+          throw std::runtime_error("Unknown argument");
         }
       }
     }
@@ -540,26 +479,20 @@ class ArgumentParser {
      * @throws std::runtime_error in case of any invalid argument
      */
     void parse_args_validate() {
-      try {
-        // Check if all positional arguments are parsed
-        std::for_each(std::begin(mPositionalArguments),
-                      std::end(mPositionalArguments),
-                      std::mem_fn(&Argument::validate));
-        // Check if all user-provided optional argument values are parsed correctly
-        std::for_each(std::begin(mOptionalArguments),
-                      std::end(mOptionalArguments),
-                      std::mem_fn(&Argument::validate));
-      } catch (const std::runtime_error& err) {
-        throw err;
-      }
+      // Check if all arguments are parsed
+      std::for_each(std::begin(mArgumentMap), std::end(mArgumentMap), [](const auto& argPair) {
+          const auto& [key, arg] = argPair;
+          arg->validate();
+      });
     }
 
     // Used by print_help.
-    size_t get_length_of_longest_argument(const std::vector<std::shared_ptr<Argument>>& aArguments) {
-      if (aArguments.empty())
+    size_t get_length_of_longest_argument() {
+      if (mArgumentMap.empty())
         return 0;
-      std::vector<size_t> argumentLengths(aArguments.size());
-      std::transform(std::begin(aArguments), std::end(aArguments), std::begin(argumentLengths), [](const auto& arg) {
+      std::vector<size_t> argumentLengths(mArgumentMap.size());
+      std::transform(std::begin(mArgumentMap), std::end(mArgumentMap), std::begin(argumentLengths), [](const auto& argPair) {
+        const auto& [key, arg] = argPair;
         const auto& names = arg->mNames;
         auto maxLength = std::accumulate(std::begin(names), std::end(names), std::string::size_type{0}, [](const auto& sum, const auto& s) {
           return sum + s.size() + 2; // +2 for ", "
@@ -569,19 +502,10 @@ class ArgumentParser {
       return *std::max_element(std::begin(argumentLengths), std::end(argumentLengths));
     }
 
-    // Used by print_help.
-    size_t get_length_of_longest_argument() {
-      const auto positionalArgMaxSize = get_length_of_longest_argument(mPositionalArguments);
-      const auto optionalArgMaxSize = get_length_of_longest_argument(mOptionalArguments);
-
-      return std::max(positionalArgMaxSize, optionalArgMaxSize);
-    }
-
     std::string mProgramName;
     std::vector<ArgumentParser> mParentParsers;
     std::vector<std::shared_ptr<Argument>> mPositionalArguments;
     std::vector<std::shared_ptr<Argument>> mOptionalArguments;
-    size_t mNextPositionalArgument = 0;
     std::map<std::string, std::shared_ptr<Argument>> mArgumentMap;
 };
 
diff --git a/test/test_compound_arguments.hpp b/test/test_compound_arguments.hpp
index a096f02..b584246 100644
--- a/test/test_compound_arguments.hpp
+++ b/test/test_compound_arguments.hpp
@@ -77,30 +77,7 @@ TEST_CASE("Parse compound toggle arguments with implicit values and nargs and ot
   program.add_argument("--input_files")
     .nargs(3);
 
-  program.parse_args({ "./test.exe", "1", "-abc", "3.14", "2.718", "2", "--input_files",
-    "a.txt", "b.txt", "c.txt", "3" });
-
-  REQUIRE(program.get<bool>("-a") == true);
-  REQUIRE(program.get<bool>("-b") == true);
-  auto c = program.get<std::vector<float>>("-c");
-  REQUIRE(c.size() == 2);
-  REQUIRE(c[0] == 3.14f);
-  REQUIRE(c[1] == 2.718f);
-  auto input_files = program.get<std::vector<std::string>>("--input_files");
-  REQUIRE(input_files.size() == 3);
-  REQUIRE(input_files[0] == "a.txt");
-  REQUIRE(input_files[1] == "b.txt");
-  REQUIRE(input_files[2] == "c.txt");
-  auto numbers = program.get<std::vector<int>>("numbers");
-  REQUIRE(numbers.size() == 3);
-  REQUIRE(numbers[0] == 1);
-  REQUIRE(numbers[1] == 2);
-  REQUIRE(numbers[2] == 3);
-  auto numbers_list = program.get<std::list<int>>("numbers");
-  REQUIRE(numbers.size() == 3);
-  REQUIRE(testutility::get_from_list(numbers_list, 0) == 1);
-  REQUIRE(testutility::get_from_list(numbers_list, 1) == 2);
-  REQUIRE(testutility::get_from_list(numbers_list, 2) == 3);
+  REQUIRE_THROWS(program.parse_args({ "./test.exe", "1", "-abc", "3.14", "2.718", "2", "--input_files", "a.txt", "b.txt", "c.txt", "3" }));
 }
 
 TEST_CASE("Parse out-of-order compound arguments", "[compound_arguments]") {
diff --git a/test/test_invalid_arguments.hpp b/test/test_invalid_arguments.hpp
index f466be8..1806816 100644
--- a/test/test_invalid_arguments.hpp
+++ b/test/test_invalid_arguments.hpp
@@ -34,5 +34,5 @@ TEST_CASE("Parse unknown optional argument", "[compound_arguments]") {
     .action([](const std::string& val) { return std::stoull(val); })
     .help("memory in MB to give the VMM when loading");
 
-  bfm.parse_args({ "./test.exe", "-om" });
+  REQUIRE_THROWS(bfm.parse_args({ "./test.exe", "-om" }));
 }
diff --git a/test/test_positional_arguments.hpp b/test/test_positional_arguments.hpp
index e69d55f..6e605f1 100644
--- a/test/test_positional_arguments.hpp
+++ b/test/test_positional_arguments.hpp
@@ -44,13 +44,7 @@ TEST_CASE("Parse positional arguments with optional arguments in the middle", "[
   program.add_argument("output").nargs(2);
   program.add_argument("--num_iterations")
     .action([](const std::string& value) { return std::stoi(value); });
-  program.parse_args({ "test", "rocket.mesh", "thrust_profile.csv", "--num_iterations", "15", "output.mesh" });
-  REQUIRE(program.get<int>("--num_iterations") == 15);
-  REQUIRE(program.get("input") == "rocket.mesh");
-  auto outputs = program.get<std::vector<std::string>>("output");
-  REQUIRE(outputs.size() == 2);
-  REQUIRE(outputs[0] == "thrust_profile.csv");
-  REQUIRE(outputs[1] == "output.mesh");
+  REQUIRE_THROWS(program.parse_args({ "test", "rocket.mesh", "thrust_profile.csv", "--num_iterations", "15", "output.mesh" }));
 }
 
 TEST_CASE("Square a number", "[positional_arguments]") {