// (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.
Reads from a compatible input.
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" ```
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.