fix: access members directly

docs/content.en/docs/features/value.md

@@ -92,6 +92,32 @@ std::cout << v.at(1);
 
 If the stored type is not `array_type`, a `type_error` is thrown.
 
+### `try_at(std::size_t i)`
+
+Performs the same operation as `at(i)`, but instead of throwing an exception on failure, it always returns a [`toml::result<T&, error_info>`]({{<ref "docs/reference/result">}}). It does not throw an exception on failure.
+
+```cpp
+toml::value v(toml::array{1,2,3});
+
+auto res1 = v.try_at(1);
+assert(res1.is_ok());
+std::cout << res1.unwrap() << std::endl;
+
+auto res5 = v.try_at(5);
+assert(res1.is_err());
+std::cout << toml::format_error(res1.unwrap_err()) << std::endl;
+```
+
+Additionally, since this `toml::result` holds a reference, it is possible to update the value.
+
+```cpp
+toml::value v(toml::array{1,2,3});
+
+auto res1 = v.try_at(1);
+assert(res1.is_ok());
+res1.unwrap() = 42;
+```
+
 #### `at(std::string key)`, `operator[](std::string key)`
 
 These are equivalent to `as_table().at(key)` and `as_table()[key]`.
@@ -105,6 +131,32 @@ v["a"] = 42;
 
 If the stored type is not `table_type`, a `type_error` is thrown.
 
+### `try_at(std::string key)`
+
+Performs the same operation as `at(key)`, but instead of throwing an exception on failure, it always returns a [`toml::result<T&, error_info>`]({{<ref "docs/reference/result">}}). It does not throw an exception on failure.
+
+```cpp
+toml::value v(toml::table{ {"a", 42}, {"b", "foo"} });
+
+auto res_a = v.try_at("a");
+assert(res_a.is_ok());
+std::cout << res_a.unwrap() << std::endl;
+
+auto res_c = v.try_at("c");
+assert(res_c.is_err());
+std::cout << toml::format_error(res_c.unwrap_err()) << std::endl;
+```
+
+Additionally, since this `toml::result` holds a reference, it is possible to update the value.
+
+```cpp
+toml::value v(toml::table{ {"a", 42}, {"b", "foo"} });
+
+auto res_a = v.try_at("a");
+assert(res_a.is_ok());
+res_a.unwrap() = 6 * 9;
+```
+
 #### `size()`
 
 Returns the length.

docs/content.en/docs/reference/value.md

@@ -585,6 +585,27 @@ Throws `std::out_of_range` if the `table` does not contain the specified element
 
 -----
 
+### `try_at(key)`
+
+```cpp
+result<std::reference_wrapper<value_type>,       error_info> try_at(const key_type& key)       noexcept;
+result<std::reference_wrapper<const value_type>, error_info> try_at(const key_type& key) const noexcept;
+```
+
+#### Return Value
+
+After casting the current `value` to a `table`, it returns the element specified by the `key`.
+
+If successful, it returns a `reference_wrapper` holding a reference to that element.
+
+If unsuccessful, it returns an `error_info` corresponding to `type_error` or `out_of_range`.
+
+#### Exceptions
+
+Does not throw.
+
+-----
+
 #### `operator[](key)`
 
 ```cpp
@@ -652,6 +673,26 @@ Throws `toml::type_error` if the stored value is not an `array`.
 
 Throws `std::out_of_range` if the specified element does not exist in the `array`.
 
+-----
+
+### `try_at(idx)`
+
+```cpp
+result<std::reference_wrapper<value_type>,       error_info> try_at(const std::size_t idx)       noexcept;
+result<std::reference_wrapper<const value_type>, error_info> try_at(const std::size_t idx) const noexcept;
+```
+
+#### Return Value
+
+After casting the current `value` to an `array`, it returns the element specified by the `idx`.
+
+If successful, it returns a `reference_wrapper` holding a reference to that element.
+
+If unsuccessful, it returns an `error_info` corresponding to `type_error` or `out_of_range`.
+
+#### Exceptions
+
+Does not throw.
 
 -----
 

docs/content.ja/docs/features/value.md

@@ -96,6 +96,32 @@ std::cout << v.at(1);
 
 格納している型が `array_type` ではなかった場合、 `type_error` を送出します。
 
+#### `try_at(std::size_t i)`
+
+`at(i)`と同様の操作をしますが、失敗時に例外を投げる代わりに、常に[`toml::result<T&, error_info>`]({{<ref "docs/reference/result">}})を返します。失敗時に例外は投げません。
+
+```cpp
+toml::value v(toml::array{1,2,3});
+
+auto res1 = v.try_at(1);
+assert(res1.is_ok());
+std::cout << res1.unwrap() << std::endl;
+
+auto res5 = v.try_at(5);
+assert(res1.is_err());
+std::cout << toml::format_error(res1.unwrap_err()) << std::endl;
+```
+
+また、この`toml::result`は成功値として参照を持つので、値を更新することも可能です。
+
+```cpp
+toml::value v(toml::array{1,2,3});
+
+auto res1 = v.try_at(1);
+assert(res1.is_ok());
+res1.unwrap() = 42;
+```
+
 #### `at(std::string key)`, `operator[](std::string key)`
 
 `as_table().at(key)`, `as_table()[key]` と同等です。
@@ -111,6 +137,32 @@ v["a"] = 42;
 
 格納している型が `table_type` ではなかった場合、 `type_error` を送出します。
 
+#### `try_at(std::string key)`
+
+`at(key)`と同様の操作をしますが、失敗時に例外を投げる代わりに、常に[`toml::result<T&, error_info>`]({{<ref "docs/reference/result">}})を返します。失敗時に例外は投げません。
+
+```cpp
+toml::value v(toml::table{ {"a", 42}, {"b", "foo"} });
+
+auto res_a = v.try_at("a");
+assert(res_a.is_ok());
+std::cout << res_a.unwrap() << std::endl;
+
+auto res_c = v.try_at("c");
+assert(res_c.is_err());
+std::cout << toml::format_error(res_c.unwrap_err()) << std::endl;
+```
+
+また、この`toml::result`は成功値として参照を持つので、値を更新することも可能です。
+
+```cpp
+toml::value v(toml::table{ {"a", 42}, {"b", "foo"} });
+
+auto res_a = v.try_at("a");
+assert(res_a.is_ok());
+res_a.unwrap() = 6 * 9;
+```
+
 #### `size()`
 
 長さを返します。

docs/content.ja/docs/reference/value.md

@@ -583,6 +583,27 @@ value_type const& at(const key_type& key) const;
 
 -----
 
+### `try_at(key)`
+
+```cpp
+result<std::reference_wrapper<value_type>,       error_info> try_at(const key_type& key)       noexcept;
+result<std::reference_wrapper<const value_type>, error_info> try_at(const key_type& key) const noexcept;
+```
+
+#### 戻り値
+
+今の`value`を`table`にキャストしたあと、`key`によって指定される要素を返します。
+
+成功した場合、その要素への参照を持つ`reference_wrapper`を返します。
+
+失敗した場合、 `type_error` または `out_of_range` に対応する `error_info` を返します。
+
+#### 例外
+
+投げません。
+
+-----
+
 #### `operator[](key)`
 
 ```cpp
@@ -652,6 +673,27 @@ value_type const& at(const std::size_t idx) const;
 
 -----
 
+### `try_at(idx)`
+
+```cpp
+result<std::reference_wrapper<value_type>,       error_info> try_at(const std::size_t idx)       noexcept;
+result<std::reference_wrapper<const value_type>, error_info> try_at(const std::size_t idx) const noexcept;
+```
+
+#### 戻り値
+
+今の`value`を`array`にキャストしたあと、`idx`によって指定される要素を返します。
+
+成功した場合、その要素への参照を持つ`reference_wrapper`を返します。
+
+失敗した場合、 `type_error` または `out_of_range` に対応する `error_info` を返します。
+
+#### 例外
+
+投げません。
+
+-----
+
 ### `operator[](idx)`
 
 ```cpp

include/toml11/result.hpp

@@ -244,13 +244,13 @@ struct result
     {
         if(other.is_ok())
         {
-            auto tmp = ::new(std::addressof(this->succ_)) success_type(other.as_ok());
+            auto tmp = ::new(std::addressof(this->succ_)) success_type(other.succ_);
             assert(tmp == std::addressof(this->succ_));
             (void)tmp;
         }
         else
         {
-            auto tmp = ::new(std::addressof(this->fail_)) failure_type(other.as_err());
+            auto tmp = ::new(std::addressof(this->fail_)) failure_type(other.fail_);
             assert(tmp == std::addressof(this->fail_));
             (void)tmp;
         }
@@ -259,13 +259,13 @@ struct result
     {
         if(other.is_ok())
         {
-            auto tmp = ::new(std::addressof(this->succ_)) success_type(std::move(other.as_ok()));
+            auto tmp = ::new(std::addressof(this->succ_)) success_type(std::move(other.succ_));
             assert(tmp == std::addressof(this->succ_));
             (void)tmp;
         }
         else
         {
-            auto tmp = ::new(std::addressof(this->fail_)) failure_type(std::move(other.as_err()));
+            auto tmp = ::new(std::addressof(this->fail_)) failure_type(std::move(other.fail_));
             assert(tmp == std::addressof(this->fail_));
             (void)tmp;
         }
@@ -276,13 +276,13 @@ struct result
         this->cleanup();
         if(other.is_ok())
         {
-            auto tmp = ::new(std::addressof(this->succ_)) success_type(other.as_ok());
+            auto tmp = ::new(std::addressof(this->succ_)) success_type(other.succ_);
             assert(tmp == std::addressof(this->succ_));
             (void)tmp;
         }
         else
         {
-            auto tmp = ::new(std::addressof(this->fail_)) failure_type(other.as_err());
+            auto tmp = ::new(std::addressof(this->fail_)) failure_type(other.fail_);
             assert(tmp == std::addressof(this->fail_));
             (void)tmp;
         }
@@ -294,13 +294,13 @@ struct result
         this->cleanup();
         if(other.is_ok())
         {
-            auto tmp = ::new(std::addressof(this->succ_)) success_type(std::move(other.as_ok()));
+            auto tmp = ::new(std::addressof(this->succ_)) success_type(std::move(other.succ_));
             assert(tmp == std::addressof(this->succ_));
             (void)tmp;
         }
         else
         {
-            auto tmp = ::new(std::addressof(this->fail_)) failure_type(std::move(other.as_err()));
+            auto tmp = ::new(std::addressof(this->fail_)) failure_type(std::move(other.fail_));
             assert(tmp == std::addressof(this->fail_));
             (void)tmp;
         }

include/toml11/value.hpp

@@ -50,6 +50,9 @@ error_info make_type_error(const basic_value<TC>&, const std::string&, const val
 template<typename TC>
 error_info make_not_found_error(const basic_value<TC>&, const std::string&, const std::string&);
 
+template<typename TC>
+error_info make_not_found_error(const basic_value<TC>&, const std::string&, const std::size_t);
+
 template<typename TC>
 void change_region_of_value(basic_value<TC>&, const basic_value<TC>&);
 
@@ -1613,6 +1616,44 @@ class basic_value
         assert(found->first == k);
         return found->second;
     }
+
+    result<std::reference_wrapper<value_type>, error_info>
+    try_at(const key_type& k) noexcept
+    {
+        if(!this->is_table())
+        {
+            return err(detail::make_type_error(*this,
+                        "toml::value::try_at(key_type)", value_t::table));
+        }
+        auto& table = this->as_table(std::nothrow);
+        const auto found = table.find(k);
+        if(found == table.end())
+        {
+            return err(detail::make_not_found_error(*this,
+                        "toml::value::try_at(key_type)", k));
+        }
+        assert(found->first == k);
+        return ok(std::ref(found->second));
+    }
+    result<std::reference_wrapper<const value_type>, error_info>
+    try_at(const key_type& k) const noexcept
+    {
+        if(!this->is_table())
+        {
+            return err(detail::make_type_error(*this,
+                        "toml::value::try_at(key_type)", value_t::table));
+        }
+        const auto& table = this->as_table(std::nothrow);
+        const auto found = table.find(k);
+        if(found == table.end())
+        {
+            return err(detail::make_not_found_error(*this,
+                        "toml::value::try_at(key_type)", k));
+        }
+        assert(found->first == k);
+        return ok(std::cref(found->second));
+    }
+
     value_type& operator[](const key_type& k)
     {
         if(this->is_empty())
@@ -1688,6 +1729,41 @@ class basic_value
         return ar.at(idx);
     }
 
+    result<std::reference_wrapper<value_type>, error_info>
+    try_at(const std::size_t& idx) noexcept
+    {
+        if(!this->is_array())
+        {
+            return err(detail::make_type_error(*this,
+                        "toml::value::try_at(key_type)", value_t::array));
+        }
+        auto& ar = this->as_array(std::nothrow);
+
+        if(ar.size() <= idx)
+        {
+            return err(detail::make_not_found_error(*this,
+                "toml::value::try_at(idx)", idx));
+        }
+        return ok(std::ref(ar[idx]));
+    }
+    result<std::reference_wrapper<const value_type>, error_info>
+    try_at(const std::size_t idx) const noexcept
+    {
+        if(!this->is_array())
+        {
+            return err(detail::make_type_error(*this,
+                        "toml::value::try_at(key_type)", value_t::array));
+        }
+        const auto& ar = this->as_array(std::nothrow);
+
+        if(ar.size() <= idx)
+        {
+            return err(detail::make_not_found_error(*this,
+                "toml::value::try_at(idx)", idx));
+        }
+        return ok(std::cref(ar[idx]));
+    }
+
     value_type&       operator[](const std::size_t idx) noexcept
     {
         // no check...
@@ -2092,6 +2168,19 @@ error_info make_not_found_error(const basic_value<TC>& v, const std::string& fna
     }
     return error_info(title, locs);
 }
+template<typename TC>
+error_info make_not_found_error(const basic_value<TC>& v, const std::string& fname, const std::size_t idx)
+{
+    if( ! v.is_array())
+    {
+        return make_type_error(v, fname, toml::value_t::array);
+    }
+    std::ostringstream oss;
+    oss << "actual length (" << v.as_array(std::nothrow).size()
+        << ") is shorter than the specified index (" << idx << ").";
+    return make_error_info(fname + ": no element corresponding to the index",
+            v, oss.str());
+}
 
 #define TOML11_DETAIL_GENERATE_COMPTIME_GETTER(ty)                              \
     template<typename TC>                                                       \

tests/test_value.cpp

@@ -1062,21 +1062,89 @@ TEST_CASE("testing array-accessors")
 {
     toml::value x({true, 42, "hoge"});
 
+    // at
+
     CHECK_UNARY(x.at(0).is_boolean());
     CHECK_UNARY(x.at(1).is_integer());
     CHECK_UNARY(x.at(2).is_string());
+    CHECK_EQ(x.at(0).as_boolean(), true);
+    CHECK_EQ(x.at(1).as_integer(), 42);
+    CHECK_EQ(x.at(2).as_string(),  std::string("hoge"));
+    CHECK_THROWS_AS(x.at(3), std::out_of_range);
 
     CHECK_UNARY(as_const(x).at(0).is_boolean());
     CHECK_UNARY(as_const(x).at(1).is_integer());
     CHECK_UNARY(as_const(x).at(2).is_string());
-
-    CHECK_EQ(x.at(0).as_boolean(), true);
-    CHECK_EQ(x.at(1).as_integer(), 42);
-    CHECK_EQ(x.at(2).as_string(),  std::string("hoge"));
-
     CHECK_EQ(as_const(x).at(0).as_boolean(), true);
     CHECK_EQ(as_const(x).at(1).as_integer(), 42);
     CHECK_EQ(as_const(x).at(2).as_string(),  std::string("hoge"));
+    CHECK_THROWS_AS(as_const(x).at(3), std::out_of_range);
+
+    // update through at
+
+    x.at(0) = false;
+    x.at(1) = 6 * 9;
+    x.at(2) = 3.14;
+
+    CHECK_UNARY(x.at(0).is_boolean());
+    CHECK_UNARY(x.at(1).is_integer());
+    CHECK_UNARY(x.at(2).is_floating());
+    CHECK_EQ(x.at(0).as_boolean(), false);
+    CHECK_EQ(x.at(1).as_integer(), 6*9);
+    CHECK_EQ(x.at(2).as_floating(),  3.14);
+
+    x.at(0) = true;
+    x.at(1) = 42;
+    x.at(2) = "hoge";
+
+    // try_at
+
+    CHECK_UNARY(x.try_at(0).is_ok());
+    CHECK_UNARY(x.try_at(1).is_ok());
+    CHECK_UNARY(x.try_at(2).is_ok());
+    CHECK_UNARY(x.try_at(0).as_ok().is_boolean());
+    CHECK_UNARY(x.try_at(1).as_ok().is_integer());
+    CHECK_UNARY(x.try_at(2).as_ok().is_string());
+    CHECK_UNARY_FALSE(x.try_at(0).is_err());
+    CHECK_UNARY_FALSE(x.try_at(1).is_err());
+    CHECK_UNARY_FALSE(x.try_at(2).is_err());
+    CHECK_EQ(x.try_at(0).as_ok().as_boolean(), true);
+    CHECK_EQ(x.try_at(1).as_ok().as_integer(), 42);
+    CHECK_EQ(x.try_at(2).as_ok().as_string(),  std::string("hoge"));
+    CHECK_UNARY(x.try_at(3).is_err());
+
+    CHECK_UNARY(as_const(x).try_at(0).is_ok());
+    CHECK_UNARY(as_const(x).try_at(1).is_ok());
+    CHECK_UNARY(as_const(x).try_at(2).is_ok());
+    CHECK_UNARY(as_const(x).try_at(0).as_ok().is_boolean());
+    CHECK_UNARY(as_const(x).try_at(1).as_ok().is_integer());
+    CHECK_UNARY(as_const(x).try_at(2).as_ok().is_string());
+    CHECK_UNARY_FALSE(as_const(x).try_at(0).is_err());
+    CHECK_UNARY_FALSE(as_const(x).try_at(1).is_err());
+    CHECK_UNARY_FALSE(as_const(x).try_at(2).is_err());
+    CHECK_EQ(as_const(x).try_at(0).as_ok().as_boolean(), true);
+    CHECK_EQ(as_const(x).try_at(1).as_ok().as_integer(), 42);
+    CHECK_EQ(as_const(x).try_at(2).as_ok().as_string(),  std::string("hoge"));
+    CHECK_UNARY(as_const(x).try_at(3).is_err());
+
+    // update through try_at
+
+    x.try_at(0).as_ok() = false;
+    x.try_at(1).as_ok() = 6 * 9;
+    x.try_at(2).as_ok() = 3.14;
+
+    CHECK_UNARY(x.at(0).is_boolean());
+    CHECK_UNARY(x.at(1).is_integer());
+    CHECK_UNARY(x.at(2).is_floating());
+    CHECK_EQ(x.at(0).as_boolean(), false);
+    CHECK_EQ(x.at(1).as_integer(), 6*9);
+    CHECK_EQ(x.at(2).as_floating(),  3.14);
+
+    x.try_at(0).as_ok() = true;
+    x.try_at(1).as_ok() = 42;
+    x.try_at(2).as_ok() = "hoge";
+
+    // operator[]
 
     CHECK_UNARY(x[0].is_boolean());
     CHECK_UNARY(x[1].is_integer());
@@ -1086,6 +1154,8 @@ TEST_CASE("testing array-accessors")
     CHECK_EQ(x[1].as_integer(), 42);
     CHECK_EQ(x[2].as_string(),  std::string("hoge"));
 
+    // -----------------------------------------------------------------------
+
     const toml::value v1(3.14);
     toml::value v2(2.71);
 
@@ -1143,13 +1213,83 @@ TEST_CASE("testing table-accessors")
     CHECK_EQ(x.count("d"), 0);
     CHECK_EQ(x.count("e"), 0);
 
+    // at
+
     CHECK_UNARY(x.at("a").is_boolean());
     CHECK_UNARY(x.at("b").is_integer());
     CHECK_UNARY(x.at("c").is_string());
-
     CHECK_EQ(x.at("a").as_boolean(), true);
     CHECK_EQ(x.at("b").as_integer(), 42);
     CHECK_EQ(x.at("c").as_string(),  std::string("hoge"));
+    CHECK_THROWS_AS(x.at("d"), std::out_of_range);
+
+    CHECK_UNARY(as_const(x).at("a").is_boolean());
+    CHECK_UNARY(as_const(x).at("b").is_integer());
+    CHECK_UNARY(as_const(x).at("c").is_string());
+    CHECK_EQ(as_const(x).at("a").as_boolean(), true);
+    CHECK_EQ(as_const(x).at("b").as_integer(), 42);
+    CHECK_EQ(as_const(x).at("c").as_string(),  std::string("hoge"));
+    CHECK_THROWS_AS(as_const(x).at("d"), std::out_of_range);
+
+    // rewrite using at
+
+    x.at("a") = false;
+    x.at("b") = 6*9;
+    x.at("c") = 3.14;
+
+    CHECK_UNARY(x.at("a").is_boolean());
+    CHECK_UNARY(x.at("b").is_integer());
+    CHECK_UNARY(x.at("c").is_floating());
+    CHECK_EQ(x.at("a").as_boolean(), false);
+    CHECK_EQ(x.at("b").as_integer(), 6*9);
+    CHECK_EQ(x.at("c").as_floating(), 3.14);
+
+    x.at("a") = true;
+    x.at("b") = 42;
+    x.at("c") = "hoge";
+
+    // try_at
+
+    CHECK_UNARY(x.try_at("a").is_ok());
+    CHECK_UNARY(x.try_at("b").is_ok());
+    CHECK_UNARY(x.try_at("c").is_ok());
+    CHECK_UNARY(x.try_at("a").as_ok().is_boolean());
+    CHECK_UNARY(x.try_at("b").as_ok().is_integer());
+    CHECK_UNARY(x.try_at("c").as_ok().is_string());
+    CHECK_EQ(x.try_at("a").as_ok().as_boolean(), true);
+    CHECK_EQ(x.try_at("b").as_ok().as_integer(), 42);
+    CHECK_EQ(x.try_at("c").as_ok().as_string(),  std::string("hoge"));
+    CHECK_UNARY(x.try_at("d").is_err());
+
+    CHECK_UNARY(as_const(x).try_at("a").is_ok());
+    CHECK_UNARY(as_const(x).try_at("b").is_ok());
+    CHECK_UNARY(as_const(x).try_at("c").is_ok());
+    CHECK_UNARY(as_const(x).try_at("a").as_ok().is_boolean());
+    CHECK_UNARY(as_const(x).try_at("b").as_ok().is_integer());
+    CHECK_UNARY(as_const(x).try_at("c").as_ok().is_string());
+    CHECK_EQ(as_const(x).try_at("a").as_ok().as_boolean(), true);
+    CHECK_EQ(as_const(x).try_at("b").as_ok().as_integer(), 42);
+    CHECK_EQ(as_const(x).try_at("c").as_ok().as_string(),  std::string("hoge"));
+    CHECK_UNARY(as_const(x).try_at("d").is_err());
+
+    // rewrite using try_at
+
+    x.try_at("a").as_ok() = false;
+    x.try_at("b").as_ok() = 6*9;
+    x.try_at("c").as_ok() = 3.14;
+
+    CHECK_UNARY(x.at("a").is_boolean());
+    CHECK_UNARY(x.at("b").is_integer());
+    CHECK_UNARY(x.at("c").is_floating());
+    CHECK_EQ(x.at("a").as_boolean(), false);
+    CHECK_EQ(x.at("b").as_integer(), 6*9);
+    CHECK_EQ(x.at("c").as_floating(), 3.14);
+
+    x.try_at("a").as_ok() = true;
+    x.try_at("b").as_ok() = 42;
+    x.try_at("c").as_ok() = "hoge";
+
+    // operator[]
 
     CHECK_UNARY(x["a"].is_boolean());
     CHECK_UNARY(x["b"].is_integer());