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Fixed a bug which caused unnecessary infinite recursion

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This commit is contained in:
Emi Simpson 2023-03-06 14:16:03 -05:00
parent 73e9771e6c
commit dfdbda4406
Signed by: Emi
GPG key ID: A12F2C2FFDC3D847
1 changed files with 37 additions and 21 deletions
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58
resolution.py
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@ -134,8 +134,8 @@ i.e. the empty clause
def next_generation(
previous_generations: KnowledgeBase_,
current_generation: KnowledgeBase_,
previous_generations: KnowledgeBase,
current_generation: KnowledgeBase,
) -> KnowledgeBase:
"""
Advance resolution by one step
@ -154,13 +154,13 @@ def next_generation(
empty list for previous generations indicates that this is the zeroth (original)
knowledge base.
>>> next_generation([
... ], [
... [IRNeg(IRProp('animal', [IRProp('Kim')]))],
... [IRNeg(IRProp('dog', [IRVar('x0')])), IRProp('animal', [IRVar('x0')])],
... [IRNeg(IRProp('cat', [IRVar('x1')])), IRProp('animal', [IRVar('x1')])],
... [IRProp('dog', [IRProp('Kim')])],
... ]) #doctest: +NORMALIZE_WHITESPACE
>>> next_generation(fset(
... ), fset(
... fset( IRNeg(IRProp('animal', (IRProp('Kim'),))) ),
... fset( IRNeg(IRProp('dog', (IRVar('x0'),))), IRProp('animal', (IRVar('x0'),)) ),
... fset( IRNeg(IRProp('cat', (IRVar('x1'),))), IRProp('animal', (IRVar('x1'),)) ),
... fset( IRProp('dog', (IRProp('Kim'),)) ),
... )) #doctest: +NORMALIZE_WHITESPACE
{
{ animal(Kim()) },
{ ¬cat(Kim()) },
@ -171,24 +171,40 @@ def next_generation(
the first generation have been moved to the previous generations knowledge base, and
the current generation contains only the results from the first call.
>>> next_generation([
... [IRNeg(IRProp('animal', [IRProp('Kim')]))],
... [IRNeg(IRProp('dog', [IRVar('x0')])), IRProp('animal', [IRVar('x0')])],
... [IRNeg(IRProp('cat', [IRVar('x1')])), IRProp('animal', [IRVar('x1')])],
... [IRProp('dog', [IRProp('Kim')])],
... ], [
... [IRNeg(IRProp('dog', [IRProp('Kim')]))],
... [IRNeg(IRProp('cat', [IRProp('Kim')]))],
... [IRProp('animal', [IRProp('Kim')])],
... ])
>>> next_generation(fset(
... fset( IRNeg(IRProp('animal', (IRProp('Kim'),))) ),
... fset( IRNeg(IRProp('dog', (IRVar('x0'),))), IRProp('animal', (IRVar('x0'),)) ),
... fset( IRNeg(IRProp('cat', (IRVar('x1'),))), IRProp('animal', (IRVar('x1'),)) ),
... fset( IRProp('dog', (IRProp('Kim'),)) ),
... ), fset(
... fset( IRNeg(IRProp('dog', (IRProp('Kim'),))) ),
... fset( IRNeg(IRProp('cat', (IRProp('Kim'),))) ),
... fset( IRProp('animal', (IRProp('Kim'),)) ),
... ))
{ { } }
The return of a knowledge base containing false (ie `[]`) indicates that resolution
has found a contradiction. In this case, there are two: One from ¬dog(Kim) and
dog(Kim), and one from animal(Kim) and ¬animal(Kim).
"""
return fset(*derive(current_generation), *derive2(current_generation, previous_generations))
Excluded from the next generation is any term which exists in a previous generation.
For example:
>>> next_generation(fset(
... ), fset(
... fset( IRNeg(IRProp('day')), IRProp('day') ),
... fset( IRProp('day') ),
... ))
{ }
This configuration could theoretically derive day() again, however, it does not,
because that is already known, and is present in the current generation.
"""
return FSet(
(derive(current_generation) | derive2(current_generation, previous_generations))
- current_generation
- previous_generations
)
def derives_false(
knowledge_base: KnowledgeBase,
previous_generations: KnowledgeBase = FSet(),