Torin Sandall 3ebbeede6c Refactor topdown evaluation/unification ...

These changes modify topdown evaluation to use a binding list that
namespaces variables. This allows topdown to propagate partially ground
ref operands into child query evaluation.

These changes also prepare topdown evaluation to support a partial
evaluation mode.

With these changes, evaluation is no longer performed in two steps
(i.e., first pass of evaluating individual terms, second pass of
evaluating built-in expressions.) Instead, evaluation assumes queries
have been rewritten to eagerly evaluate refs and comprehension. This
way, ref and comprehension bindings do not have to be maintained
separately: they are handled by the normal variable binding list.

This commit contains some breaking changes to the topdown APIs,
namely...

1. Truth explanation has been removed. This feature was not used and the
tracing changes broke it. We can revisit in future if necessary.

2. Data indexing has been removed. Data indexing can be re-added in
future if necessary however it should be handled outside of topdown to
avoid potential memory leaks.

3. Built-in functions produce at-most-one output now. Functions that
used to produce multiple outputs (e.g., io.jwt.decode) can produce a
composite value if they need to.

Fixes #131

2017-11-09 09:07:48 -08:00

..

types_test.go

Refactor topdown evaluation/unification

2017-11-09 09:07:48 -08:00

types.go

Refactor topdown evaluation/unification

2017-11-09 09:07:48 -08:00