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api/basic_json_view/cbegin.md

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+# <small>nlohmann::basic_json_view::</small>cbegin
+
+```cpp
+iterator cbegin() const noexcept;
+```
+
+Returns an iterator to the first element, in [document order](begin.md). Equivalent to [`begin()`](begin.md): a view
+is always read-only, so `#!cpp const_iterator` and `#!cpp iterator` are the same type, and `cbegin()` exists only so
+that generic code that expects a `cbegin()`/`cend()` pair works with a view too.
+
+## Return value
+
+Iterator to the first element; identical to what [`begin()`](begin.md) returns.
+
+## Exception safety
+
+No-throw guarantee: this function never throws exceptions.
+
+## Complexity
+
+Constant.
+
+## Examples
+
+??? example
+
+    The example below sums many measurements with `std::accumulate`, using `cbegin()`/[`cend()`](cend.md) as the
+    range -- the same way it would for any standard container -- without ever materializing the whole array into a
+    `BasicJsonType` value.
+
+    ```cpp
+    #include <iostream>
+    #include <numeric>
+    #include <nlohmann/json_view.hpp>
+    
+    using json_document = nlohmann::json_document;
+    using json_view = nlohmann::json_view;
+    
+    int main()
+    {
+        // sum many measurements with std::accumulate; cbegin()/cend() (identical
+        // to begin()/end() here -- the view is always read-only) let the view be
+        // used with standard algorithms without ever materializing the whole
+        // array into a nlohmann::json value
+        json_document measurements = json_document::parse("[3, 1, 4, 1, 5, 9, 2, 6]");
+        const auto values = measurements.root();
+    
+        const int sum = std::accumulate(values.cbegin(), values.cend(), 0,
+                                        [](int total, const json_view & v)
+        {
+            return total + v.materialize().get<int>();
+        });
+    
+        std::cout << sum << '\n';
+    }
+    
+    ```
+
+    Output:
+
+    ```json
+    31
+    
+    ```
+
+## See also
+
+- [begin](begin.md) - returns an iterator to the first element
+- [cend](cend.md) - returns a const iterator to one past the last element
+- [`BasicJsonType::cbegin`](../basic_json/cbegin.md) - the corresponding function of `basic_json`
+
+## Version history
+
+- Added in version 3.13.0.