NAME
    Types::Serialiser - simple data types for common serialisation formats

SYNOPSIS
DESCRIPTION
    This module provides some extra datatypes that are used by common
    serialisation formats such as JSON or CBOR. The idea is to have a
    repository of simple/small constants and containers that can be shared
    by different implementations so they become interoperable between each
    other.

SIMPLE SCALAR CONSTANTS
    Simple scalar constants are values that are overloaded to act like
    simple Perl values, but have (class) type to differentiate them from
    normal Perl scalars. This is necessary because these have different
    representations in the serialisation formats.

  BOOLEANS (Types::Serialiser::Boolean class)
    This type has only two instances, true and false. A natural
    representation for these in Perl is 1 and 0, but serialisation formats
    need to be able to differentiate between them and mere numbers.

    $Types::Serialiser::true, Types::Serialiser::true
        This value represents the "true" value. In most contexts is acts
        like the number 1. It is up to you whether you use the variable form
        ($Types::Serialiser::true) or the constant form
        ("Types::Serialiser::true").

        The constant is represented as a reference to a scalar containing 1
        - implementations are allowed to directly test for this.

    $Types::Serialiser::false, Types::Serialiser::false
        This value represents the "false" value. In most contexts is acts
        like the number 0. It is up to you whether you use the variable form
        ($Types::Serialiser::false) or the constant form
        ("Types::Serialiser::false").

        The constant is represented as a reference to a scalar containing 0
        - implementations are allowed to directly test for this.

    $is_bool = Types::Serialiser::is_bool $value
        Returns true iff the $value is either $Types::Serialiser::true or
        $Types::Serialiser::false.

        For example, you could differentiate between a perl true value and a
        "Types::Serialiser::true" by using this:

           $value && Types::Serialiser::is_bool $value

    $is_true = Types::Serialiser::is_true $value
        Returns true iff $value is $Types::Serialiser::true.

    $is_false = Types::Serialiser::is_false $value
        Returns false iff $value is $Types::Serialiser::false.

  ERROR (Types::Serialiser::Error class)
    This class has only a single instance, "error". It is used to signal an
    encoding or decoding error. In CBOR for example, and object that
    couldn't be encoded will be represented by a CBOR undefined value, which
    is represented by the error value in Perl.

    $Types::Serialiser::error, Types::Serialiser::error
        This value represents the "error" value. Accessing values of this
        type will throw an exception.

        The constant is represented as a reference to a scalar containing
        "undef" - implementations are allowed to directly test for this.

    $is_error = Types::Serialiser::is_error $value
        Returns false iff $value is $Types::Serialiser::error.

NOTES FOR XS USERS
    The recommended way to detect whether a scalar is one of these objects
    is to check whether the stash is the "Types::Serialiser::Boolean" or
    "Types::Serialiser::Error" stash, and then follow the scalar reference
    to see if it's 1 (true), 0 (false) or "undef" (error).

    While it is possible to use an isa test, directly comparing stash
    pointers is faster and guaranteed to work.

BUGS
    The use of overload makes this module much heavier than it should be (on
    my system, this module: 4kB RSS, overload: 260kB RSS).

SEE ALSO
    Currently, JSON::XS and CBOR::XS use these types.

AUTHOR
     Marc Lehmann <schmorp@schmorp.de>
     http://home.schmorp.de/