Generator

Description

The Generator is the most fundamental concept. A Generator has a member function, generate, that accepts an OutputIterator and returns bool as its result. The iterator receives the data being generated. The Generator's generate member function returns true if the generator succeeds. Each Generator can represent a specific pattern or algorithm, or it can be a more complex generator formed as a composition of other Generators.

Notation

g: A Generator.
G: A Generator type.
OutIter: An OutputIterator type.
sink: An OutputIterator instance.
Context: The generator's Context type.
context: The generator's Context, or unused.
delimit: A delimiter Generator, or unused.
attrib: A Compatible Attributes, or unused.

Valid Expressions

In the expressions below, the behavior of the generator, g, as well as how delimit and attrib are handled by g, are left unspecified in the base Generator concept. These are specified in subsequent, more refined concepts and by the actual models thereof.

For any Generator the following expressions must be valid:

Expression	Semantics	Return type
g.generate(sink, context, delimit, attrib)	Generate the output sequence by inserting the generated characters/tokens into `sink`. Use the `delimit` generator for delimiting. Return `true` if successful, otherwise return `false`.	`bool`
`g.what(context)`	Get information about a Generator.	`info`

Expression

Semantics

Return type

g.generate(sink, context, delimit, attrib)

Generate the output sequence by inserting the generated characters/tokens into sink. Use the delimit generator for delimiting. Return true if successful, otherwise return false.

bool

g.what(context)

Get information about a Generator.

info

Type Expressions

Expression	Description
`G::template attribute<Context>::type`	The Generator's attribute.
`traits::is_generator<G>::type`	Metafunction that evaluates to `mpl::true_` if a certain type, `G` is a Generator, `mpl::false_` otherwise (See MPL Boolean Constant).
`G::properties`	An `mpl::int_` (See MPL Integral Constant) holding a value from the `karma::generator_properties` enumeration. The default value is `generator_properties::no_properties`

Postcondition

Upon return from g.generate the following post conditions should hold:

On successful generation, sink receives the generated characters/tokens sequence.
No pre-delimits: delimit characters/tokens will not be emitted in front of any other output.
The attribute attrib has not been modified.

Models

All generators in Spirit.Karma are models of the Generator concept.