monoidal categories

A 2012 paper by Peter Selinger-era category theorists, 'Monoidal computer I: Basic computability by string diagrams', is drawing fresh attention. The work reformulates basic computability theory using monoidal categories and string diagrams, an alternative graphical language to Turing machines and lambda calculus. Readers are revisiting the arXiv paper, discussing how diagrammatic approaches can express recursion and universal computation, and debating whether the formalism offers practical insight for modern programming language theory and quantum computing.