Idea
- string diagrams constitute a graphical calculus for expressing operations in monoidal categories.
- think objects in a monoidal category as strings and of morphisms from one tensor product to another as a node
Variants
- additional extra structures on monoidal categories can be represented by encoding further geometric properties of string diagrams.
- traced: bending an output string around to connect to an input
- spherical: all strings behave as if drawn on a sphere
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