On Wed, 7 May 2014, Johannes Hölzl wrote:

* Theorems about complex numbers are now stated only using Re and Im, the 
Complex
 constructor is not used anymore. It is possible to use primcorec to defined the
 behaviour of a complex-valued function.

This is also a surprising application of primcorec!

That is indeed very nice. Is that a new invention or an old trick that every category theorist knows?

In mathematics books / lectures there is usually some handwaving only, to justify why it is possible to define functions on complex by specifying the observation of Re/Im.


        Makarius
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