Discrete functions are an integral part of numerous areas of research in mathematics and computer science. Efficient processing of such functions in a computer requires an appropriate representation. A very effective representation is decision diagrams, which are suitable for software processing. In the paper, we present the Templated Decision Diagram Library (TeDDy), which implements Binary Decision Diagrams and Multi-valued Decision Diagrams. These allow the efficient representation of Boolean functions, Multiple-valued logic functions, and integer functions. The library’s core uses C++ language templates that enable a universal implementation for all types of diagrams offered without loss of runtime efficiency or duplication of code. The library consists of a module for the general manipulation of decision diagrams and a module that contains algorithms aimed at reliability analysis based on decision diagrams. Compared to other libraries, the added value of our library is in the second module dedicated to reliability analysis.