Type Checker for Simply Typed Lambda Calculus

This paper addresses the design and implementation of a visualization tool for type checking terms of simply typed lambda calculus. Motivated by the need for a user-friendly and effective tool to understand the type-checking process of programs within this system, we chose to use Elm language to implement a tool. The tool includes step-by-step construction of the type-checking tree, with the ability to control certain aspects of the visualization, such as the abbreviation of context and the displaying of rule names used. A successful usability test of the system highlights its effectiveness in improving understanding of simply typed lambda calculus and its ability to provide a clear and interactive interface for users. This tool can be a useful teaching aid in university courses dedicated to type theory.