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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( def next_generation(
previous_generations: KnowledgeBase_, previous_generations: KnowledgeBase,
current_generation: KnowledgeBase_, current_generation: KnowledgeBase,
) -> KnowledgeBase: ) -> KnowledgeBase:
""" """
Advance resolution by one step Advance resolution by one step
@ -154,13 +154,13 @@ def next_generation(
empty list for previous generations indicates that this is the zeroth (original) empty list for previous generations indicates that this is the zeroth (original)
knowledge base. knowledge base.
>>> next_generation([ >>> next_generation(fset(
... ], [ ... ), fset(
... [IRNeg(IRProp('animal', [IRProp('Kim')]))], ... fset( IRNeg(IRProp('animal', (IRProp('Kim'),))) ),
... [IRNeg(IRProp('dog', [IRVar('x0')])), IRProp('animal', [IRVar('x0')])], ... fset( IRNeg(IRProp('dog', (IRVar('x0'),))), IRProp('animal', (IRVar('x0'),)) ),
... [IRNeg(IRProp('cat', [IRVar('x1')])), IRProp('animal', [IRVar('x1')])], ... fset( IRNeg(IRProp('cat', (IRVar('x1'),))), IRProp('animal', (IRVar('x1'),)) ),
... [IRProp('dog', [IRProp('Kim')])], ... fset( IRProp('dog', (IRProp('Kim'),)) ),
... ]) #doctest: +NORMALIZE_WHITESPACE ... )) #doctest: +NORMALIZE_WHITESPACE
{ {
{ animal(Kim()) }, { animal(Kim()) },
{ ¬cat(Kim()) }, { ¬cat(Kim()) },
@ -171,24 +171,40 @@ def next_generation(
the first generation have been moved to the previous generations knowledge base, and the first generation have been moved to the previous generations knowledge base, and
the current generation contains only the results from the first call. the current generation contains only the results from the first call.
>>> next_generation([ >>> next_generation(fset(
... [IRNeg(IRProp('animal', [IRProp('Kim')]))], ... fset( IRNeg(IRProp('animal', (IRProp('Kim'),))) ),
... [IRNeg(IRProp('dog', [IRVar('x0')])), IRProp('animal', [IRVar('x0')])], ... fset( IRNeg(IRProp('dog', (IRVar('x0'),))), IRProp('animal', (IRVar('x0'),)) ),
... [IRNeg(IRProp('cat', [IRVar('x1')])), IRProp('animal', [IRVar('x1')])], ... fset( IRNeg(IRProp('cat', (IRVar('x1'),))), IRProp('animal', (IRVar('x1'),)) ),
... [IRProp('dog', [IRProp('Kim')])], ... fset( IRProp('dog', (IRProp('Kim'),)) ),
... ], [ ... ), fset(
... [IRNeg(IRProp('dog', [IRProp('Kim')]))], ... fset( IRNeg(IRProp('dog', (IRProp('Kim'),))) ),
... [IRNeg(IRProp('cat', [IRProp('Kim')]))], ... fset( IRNeg(IRProp('cat', (IRProp('Kim'),))) ),
... [IRProp('animal', [IRProp('Kim')])], ... fset( IRProp('animal', (IRProp('Kim'),)) ),
... ]) ... ))
{ { } } { { } }
The return of a knowledge base containing false (ie `[]`) indicates that resolution 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 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). 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( def derives_false(
knowledge_base: KnowledgeBase, knowledge_base: KnowledgeBase,
previous_generations: KnowledgeBase = FSet(), previous_generations: KnowledgeBase = FSet(),