// (1)
template<typename InputType>
static bool accept(InputType&& i,
                   const bool ignore_comments = false);

// (2)
template<typename IteratorType>
static bool accept(IteratorType first, IteratorType last,
                   const bool ignore_comments = false);

Checks whether the input is valid JSON.

1. Reads from a compatible input.

2. Reads from a pair of character iterators

   The value_type of the iterator must be an integral type with size of 1, 2 or 4 bytes, which will be interpreted respectively as UTF-8, UTF-16 and UTF-32.

Unlike the parse function, this function neither throws an exception in case of invalid JSON input (i.e., a parse error) nor creates diagnostic information.

InputType : A compatible input, for instance:

- an `std::istream` object
- a `FILE` pointer (must not be null)
- a C-style array of characters
- a pointer to a null-terminated string of single byte characters
- a `std::string`
- an object `obj` for which `begin(obj)` and `end(obj)` produces a valid pair of iterators.

IteratorType : a compatible iterator type, for instance.

- a pair of `std::string::iterator` or `std::vector<std::uint8_t>::iterator`
- a pair of pointers such as `ptr` and `ptr + len`

i (in) : Input to parse from.

ignore_comments (in) : whether comments should be ignored and treated like whitespace (#!cpp true) or yield a parse error (#!cpp false); (optional, #!cpp false by default)

first (in) : iterator to start of character range

last (in) : iterator to end of character range

Whether the input is valid JSON.

Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

Linear in the length of the input. The parser is a predictive LL(1) parser.

(1) A UTF-8 byte order mark is silently ignored.

!!! danger "Runtime assertion"

The precondition that a passed `#!cpp FILE` pointer must not be null is enforced with a
[runtime assertion](../../features/assertions.md).

??? example

The example below demonstrates the `accept()` function reading from a string.

```cpp
--8<-- "examples/accept__string.cpp"
```

Output:

```json
--8<-- "examples/accept__string.output"
```

• parse - deserialize from a compatible input
• operator>> - deserialize from stream

• Added in version 3.0.0.
• Ignoring comments via ignore_comments added in version 3.9.0.

!!! warning "Deprecation"

Overload (2) replaces calls to `accept` with a pair of iterators as their first parameter which has been
deprecated in version 3.8.0. This overload will be removed in version 4.0.0. Please replace all calls like
`#!cpp accept({ptr, ptr+len}, ...);` with `#!cpp accept(ptr, ptr+len, ...);`.

You should be warned by your compiler with a `-Wdeprecated-declarations` warning if you are using a deprecated
function.