24.7 Stepping through the valuator

Mutator function: Marpa_Step_Type marpa_v_step ( Marpa_Value v)

Steps through the tree in depth-first, left-to-right order. On success, does the following:

• Takes the valuator to the next step in its life cycle.
• Sets and returns the step type, which is a non-negative integer. The C type for a step type is Marpa_Step_Type.

The step type tells the application how it expected to act on the step. See Valuator step types. Steps are often referred to along with their step type so that, for example, we say “a MARPA_STEP_RULE step” to refer to a step whose step type is MARPA_STEP_RULE.

When the iteration through the steps is finished, the step type is MARPA_STEP_INACTIVE. At this point, we say that the valuator is inactive. Once a valuator becomes inactive, it stays inactive.

Return value: On success, a Marpa_Step_Type, which always be a non-negative integer. On hard failure, -2.