From d73bc6076c5d1b914e955075d511ab8bc749ee65 Mon Sep 17 00:00:00 2001
From: ToruNiina <niina.toru.68u@gmail.com>
Date: Sat, 28 Sep 2019 16:16:44 +0900
Subject: [PATCH 1/3] feat: add basic_value::at(key) and at(idx)

---
 toml/value.hpp | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/toml/value.hpp b/toml/value.hpp
index 3d24c83..cdb9506 100644
--- a/toml/value.hpp
+++ b/toml/value.hpp
@@ -1567,6 +1567,28 @@ class basic_value
         return std::move(this->table_.value());
     }
 
+    // accessors =============================================================
+    //
+    // may throw type_error or out_of_range
+    //
+    value_type&       at(const key& k)
+    {
+        return this->as_table().at(k);
+    }
+    value_type const& at(const key& k) const
+    {
+        return this->as_table().at(k);
+    }
+
+    value_type&       at(const std::size_t idx)
+    {
+        return this->as_array().at(idx);
+    }
+    value_type const& at(const std::size_t idx) const
+    {
+        return this->as_array().at(idx);
+    }
+
     source_location location() const
     {
         return source_location(this->region_info_.get());

From babb6ab3fe9ce061fbfdabd13d01e1624c256453 Mon Sep 17 00:00:00 2001
From: ToruNiina <niina.toru.68u@gmail.com>
Date: Sat, 28 Sep 2019 16:22:01 +0900
Subject: [PATCH 2/3] test: add test case for basic_value::at

---
 tests/test_value.cpp | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/tests/test_value.cpp b/tests/test_value.cpp
index a0d32c6..8c8c70c 100644
--- a/tests/test_value.cpp
+++ b/tests/test_value.cpp
@@ -905,3 +905,32 @@ BOOST_AUTO_TEST_CASE(test_value_empty)
     BOOST_CHECK_THROW(v1.as_array(),           toml::type_error);
     BOOST_CHECK_THROW(v1.as_table(),           toml::type_error);
 }
+
+
+BOOST_AUTO_TEST_CASE(test_value_at)
+{
+    {
+        toml::value v1{{"foo", 42}, {"bar", 3.14}, {"baz", "qux"}};
+
+        BOOST_TEST(v1.at("foo").as_integer()  == 42);
+        BOOST_TEST(v1.at("bar").as_floating() == 3.14);
+        BOOST_TEST(v1.at("baz").as_string()   == "qux");
+
+        BOOST_CHECK_THROW(v1.at(0), toml::type_error);
+        BOOST_CHECK_THROW(v1.at("quux"), std::out_of_range);
+    }
+
+
+    {
+        toml::value v1{1,2,3,4,5};
+
+        BOOST_TEST(v1.at(0).as_integer() == 1);
+        BOOST_TEST(v1.at(1).as_integer() == 2);
+        BOOST_TEST(v1.at(2).as_integer() == 3);
+        BOOST_TEST(v1.at(3).as_integer() == 4);
+        BOOST_TEST(v1.at(4).as_integer() == 5);
+
+        BOOST_CHECK_THROW(v1.at("foo"), toml::type_error);
+        BOOST_CHECK_THROW(v1.at(5),     std::out_of_range);
+    }
+}

From 4bb8045c84c9b155427d306c7087950fab59721e Mon Sep 17 00:00:00 2001
From: ToruNiina <niina.toru.68u@gmail.com>
Date: Sat, 28 Sep 2019 16:31:45 +0900
Subject: [PATCH 3/3] doc: add `basic_value::at`.

---
 README.md | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/README.md b/README.md
index 81e0a53..93c0a13 100644
--- a/README.md
+++ b/README.md
@@ -454,6 +454,22 @@ class value {
 } // toml
 ```
 
+### `at()`
+
+You can access to the element of a table and an array by `toml::basic_value::at`.
+
+```cpp
+const toml::value v{1,2,3,4,5};
+std::cout << v.at(2).as_integer() << std::endl; // 3
+
+const toml::value v{{"foo", 42}, {"bar", 3.14}};
+std::cout << v.at("foo").as_integer() << std::endl; // 42
+```
+
+If an invalid key (integer for a table, string for an array), it throws
+`toml::type_error` for the conversion. If the provided key is out-of-range,
+it throws `std::out_of_range`.
+
 ## Checking value type
 
 You can check the type of a value by `is_xxx` function.