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doc/mkdocs/docs/api/basic_json/number_integer_t.md

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+# basic_json::number_integer_t
+
+```cpp
+using number_integer_t = NumberIntegerType;
+```
+
+The type used to store JSON numbers (integers).
+
+[RFC 7159](http://rfc7159.net/rfc7159) describes numbers as follows:
+> The representation of numbers is similar to that used in most
+> programming languages. A number is represented in base 10 using decimal
+> digits. It contains an integer component that may be prefixed with an
+> optional minus sign, which may be followed by a fraction part and/or an
+> exponent part. Leading zeros are not allowed. (...) Numeric values that
+> cannot be represented in the grammar below (such as Infinity and NaN)
+> are not permitted.
+
+This description includes both integer and floating-point numbers.
+However, C++ allows more precise storage if it is known whether the number
+is a signed integer, an unsigned integer or a floating-point number.
+Therefore, three different types, `number_integer_t`, 
+[`number_unsigned_t`](number_unsigned_t.md) and [`number_float_t`](number_float_t.md) are used.
+
+To store integer numbers in C++, a type is defined by the template
+parameter `NumberIntegerType` which chooses the type to use.
+
+## Notes
+
+#### Default type
+
+With the default values for `NumberIntegerType` (`std::int64_t`), the default
+value for `number_integer_t` is:
+
+```cpp
+std::int64_t
+```
+
+#### Default behavior
+
+- The restrictions about leading zeros is not enforced in C++. Instead,
+  leading zeros in integer literals lead to an interpretation as octal
+  number. Internally, the value will be stored as decimal number. For
+  instance, the C++ integer literal `010` will be serialized to `8`.
+  During deserialization, leading zeros yield an error.
+- Not-a-number (NaN) values will be serialized to `null`.
+
+#### Limits
+
+[RFC 7159](http://rfc7159.net/rfc7159) specifies:
+> An implementation may set limits on the range and precision of numbers.
+
+When the default type is used, the maximal integer number that can be
+stored is `9223372036854775807` (INT64_MAX) and the minimal integer number
+that can be stored is `-9223372036854775808` (INT64_MIN). Integer numbers
+that are out of range will yield over/underflow when used in a
+constructor. During deserialization, too large or small integer numbers
+will be automatically be stored as [`number_unsigned_t`](number_unsigned_t.md)
+or [`number_float_t`](number_float_t.md).
+
+[RFC 7159](http://rfc7159.net/rfc7159) further states:
+> Note that when such software is used, numbers that are integers and are
+> in the range \f$[-2^{53}+1, 2^{53}-1]\f$ are interoperable in the sense
+> that implementations will agree exactly on their numeric values.
+
+As this range is a subrange of the exactly supported range [INT64_MIN,
+INT64_MAX], this class's integer type is interoperable.
+
+#### Storage
+
+Integer number values are stored directly inside a `basic_json` type.
+
+## Version history
+
+- Added in version 1.0.0.