SWI-Prolog offers a comprehensive free Prolog environment.

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Installation and Setup

Once SWI-Prolog has been installed, install lanchain-prolog using pip: 
pip install langchain-prolog

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Tools

The PrologTool class allows the generation of langchain tools that use Prolog rules to generate answers. 
from langchain_prolog import PrologConfig, PrologTool
See a usage example. See the same guide for usage examples of PrologRunnable, which allows the generation of LangChain runnables that use Prolog rules to generate answers.