In this web content, the author explains how IEEE-754 floating point subtraction is functionally complete, meaning that any binary circuit can be constructed using only floating point subtraction. The author dissects the IEEE 754-2019 standard to explain the rules regarding sign bits and zero values. They then demonstrate how subtraction of zero values can be used to create an IMPLY gate, which is functionally complete. The author goes on to show examples of building other logical gates, such as NOT, OR, AND, and XOR gates, using only subtraction operations. The content also includes an example of implementing an integer addition circuit using floating point operations in Rust.
https://orlp.net/blog/subtraction-is-functionally-complete/