Before this commit, each node was responsible for computing the value of
its |resultIndex| property in the |computeVarIndices| pass. This was
possible because |resultIndex| was always equal to |index.result|,
meaning that nodes always wrote their match results to the top of the
stack.
This behavior would cause problems in the future where nodes will use
the stack also for storing positions. Parent nodes storing position on
the stack would have to copy their childs' match results from the top of
the stack to some position below where parent's match result would be
expected. There would be no way to tell the children to place their
match result somewhere else than the top of the stack and avoid copying.
This commit fixes the described problem by shifting the responsibility
for setting the value of node's |resultIndex| property to its parent.
This way it can direct its child to place its result wherever it wants
to.
This commit replaces all variable name computations in |computeVarNames|
and |computeParams| passes by computations of indices. The actual names
are computed later in the |generateCode| pass.
This change makes the code generator the only place that deals with the
actual variable names, making them easier to change for example.
The code generator code seems bit more complicated after the change, but
this complexity will pay off (and mostly disappear) later.
David Majda