graphical programming languages deserve formal semantics
Graphical programming languages have been of perennial interest to programmers: they are intuitive even for end-users without software development training, and they are closer to the digrammatic descriptions found across many branches of engineering. Graphical programming semantics is traditionally a semi-formal field; in contrast, textual programming semantics has benefitted from formal categorical structures such as monads and premonoidal categories. String Diagrams for Premonoidal Categories advances the idea that graphical programming languages can be given semantics with the same formal techniques as their textual counterparts.
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