Casting int to nat in Isabelle

问题

How can I cast an int to nat in Isabelle when I'm sure that it is positive?

value "((-10)::int) mod 3"

for example gives 2 and if I'm correct any application of modulo on an int should result in a nat.

Unfortunately the type signature of modulo is 'a => 'a => 'a so I cannot fix 3 to a nat beforehand and the result will be an int.

回答1:

You can use value "nat (((-10)::int) mod 3)".

来源：https://stackoverflow.com/questions/57027062/casting-int-to-nat-in-isabelle