1. Prolog Visualizer
Tutorial

2. Visualization
Program
Controls
Examples

3. Step 0 of 144
This is where you start
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Initial goal A copy of the program
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Dashed box
indicates the current
state of the search
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Unifying
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Unification failed because the names
of the clauses are different
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Failed rules are crossed out
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These rules failed too
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But not this rule
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substitution
before
after
Applying the substitution,
you get a new rule
This rule unifies with the goal
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Current goal is
duplicated here for
better readability
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Body of the rule after substitution
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grandfather(X, Y) is
replaced by father(X, Z)
and father(Z, Y).
these are the new goals
Current state has changed
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The grey path shows
where you came from
current goal is in bold
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Unifying
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This rule also succeeds
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18. This is a partial solution
If X is orville, any Y such that
father(abe, Y) will be a solution
father(Z, Y) is the is new goal. After the
substitution (X = oriville, Z = abe), it
becomes father(abe, Y)
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19. Current state has changed
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20. Unifying
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21. Succeeded
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22. This leads to a solution
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23. Backtrack
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24. More solutions…
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25. …