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The archetypal application needs
a value object (or
valuator) to produce
the value of the parse tree.
To create a valuator, use the
marpa_v_new()
method.
The application is required to maintain the stack,
and the application is also required to implement
most of the semantics, including the evaluation
of rules.
Libmarpa’s valuator provides instructions to
the application on how to manipulate the stack.
To iterate through this series of instructions,
use the
marpa_v_step()
method.
When successful, marpa_v_step()
returns the type
of step.
Most step types have values associated with them.
See Basic step accessors,
see How to use the valuator, and
see Stepping through the valuator.
When a valuator is no longer in use, its memory can be freed
using the
marpa_v_unref()
method.