From 39c720e6c094b959f6916ed5ea2b465a041f12c0 Mon Sep 17 00:00:00 2001
From: Mio <a771644612@live.com>
Date: Tue, 6 Aug 2019 20:48:51 +0800
Subject: [PATCH 1/2] Add a mIsRquired field

---
 include/argparse.hpp | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/argparse.hpp b/include/argparse.hpp
index 7411918..96e453d 100644
--- a/include/argparse.hpp
+++ b/include/argparse.hpp
@@ -102,6 +102,11 @@ public:
     return *this;
   }
 
+  Argument& required() {
+    mIsRequired = true;
+    return *this;
+  }
+
   Argument& implicit_value(std::any aImplicitValue) {
     mImplicitValue = std::move(aImplicitValue);
     mNumArgs = 0;
@@ -158,6 +163,16 @@ public:
       }
       else {
         // TODO: check if an implicit value was programmed for this argument
+        if (!mIsUsed && !mDefaultValue.has_value() && mIsRequired) {
+          std::stringstream stream;
+          stream << "error: " << mNames[0] << ": required.";
+          throw std::runtime_error(stream.str());
+        }
+        if (mIsUsed && mIsRequired && mValues.size() == 0) {
+          std::stringstream stream;
+          stream << "error: " << mUsedName << ": no value provided.";
+          throw std::runtime_error(stream.str());
+        }
       }
     }
     else {
@@ -298,6 +313,7 @@ public:
     std::vector<std::string> mRawValues;
     size_t mNumArgs = 1;
     bool mIsOptional = false;
+    bool mIsRequired = false;
     bool mIsUsed = false; // relevant for optional arguments. True if used by user
 
   public:

From 47122880860507d0433482e2d3ae34d1a3d243db Mon Sep 17 00:00:00 2001
From: Mio <a771644612@live.com>
Date: Tue, 6 Aug 2019 20:52:31 +0800
Subject: [PATCH 2/2] Change the format of required arguments

---
 include/argparse.hpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/argparse.hpp b/include/argparse.hpp
index 96e453d..bece74c 100644
--- a/include/argparse.hpp
+++ b/include/argparse.hpp
@@ -194,7 +194,11 @@ public:
   friend std::ostream& operator<<(std::ostream& stream, const Argument& argument) {
     std::stringstream nameStream;
     std::copy(std::begin(argument.mNames), std::end(argument.mNames), std::ostream_iterator<std::string>(nameStream, " "));
-    return stream << nameStream.str() << "\t" << argument.mHelp << "\n";
+	stream << nameStream.str() << "\t" << argument.mHelp;
+    if (argument.mIsRequired)
+      stream << "[Required]";
+    stream << "\n";
+    return stream;
   }