Jussi Piitulainen <jussi.piitulai...@helsinki.fi>: > Manolo Martínez writes: >> On 03/30/16 at 01:40pm, Jussi Piitulainen wrote: >>> Yes, and most many-to-one mappings are *not* surjective. >> >> Well, I don't know about most, there are uncountably many surjective >> and non-surjective many-to-one mappings :) > > Ok, safer to say that some many-to-one mappings are not surjective. > > I was thinking of finite sets, and not even really thinking. But even > with infinite domain and infinite codomain, there can be uncountably > many mappings without any of them being a surjection - just have the > codomain be a larger infinity.
I don't even know if you can say much about the cardinality (or countability) of mappings. The general set of mappings can't exist. The *class* of mappings does exist in some set theories, but I don't believe classes have cardinality. Marko -- https://mail.python.org/mailman/listinfo/python-list
