1# basic_json::diff 2 3```cpp 4static basic_json diff(const basic_json& source, 5 const basic_json& target); 6``` 7 8Creates a [JSON Patch](http://jsonpatch.com) so that value `source` can be changed into the value `target` by calling 9[`patch`](patch.md) function. 10 11For two JSON values `source` and `target`, the following code yields always `#!cpp true`: 12```cpp 13source.patch(diff(source, target)) == target; 14``` 15 16## Parameters 17 18`source` (in) 19: JSON value to compare from 20 21`target` (in) 22: JSON value to compare against 23 24## Return value 25 26a JSON patch to convert the `source` to `target` 27 28## Exception safety 29 30Strong guarantee: if an exception is thrown, there are no changes in the JSON value. 31 32## Complexity 33 34Linear in the lengths of `source` and `target`. 35 36## Note 37 38Currently, only `remove`, `add`, and `replace` operations are generated. 39 40## Example 41 42??? example 43 44 The following code shows how a JSON patch is created as a diff for two JSON values. 45 46 ```cpp 47 --8<-- "examples/diff.cpp" 48 ``` 49 50 Output: 51 52 ```json 53 --8<-- "examples/diff.output" 54 ``` 55 56## Version history 57 58- Added in version 2.0.0. 59