Fix for unify algorithm in logic.py - #1101
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Unify algorithm fixed by performing a perform a cascade substitution when a new mapping is added This issue was already known and fixed in the aima-java repo.
updated documentation for cascade_substitution function in logic.py
antmarakis
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Aug 16, 2019
dj5x5
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Jul 17, 2025
* Fix issue aimacode#1053 Unify algorithm fixed by performing a perform a cascade substitution when a new mapping is added This issue was already known and fixed in the aima-java repo. * added two more test in test_logic.py updated documentation for cascade_substitution function in logic.py * Fixed brackets missing in test_logic.py for the new test * Fixed typo error, missing space and double quotes for docstrings * comments changed to cascade_substitution function in logic.py
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These commits should resolve issue (#1053)
It seems that this bug is well known in the aima-java repo but was not corrected in the aima-python repo. In the
unify_var(var, x, s)method a cascade_substitution must be perform after adding a new mapping var/x to the substitution set 's' as can be seen from the unification algorithm developed in java in the aima-java repo.