[Jprogramming] more fork examples

[Don Guinn]

In an algebra course in college we formally rebuilt arithmetic from very
basics. We had to define counting number addition in terms of repeated
incrementing. Like this in J:

   increment =: >:

   increment 3

4

   plus =: increment ^:

   3 plus 4

7
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​And then we went on to define decrement in terms of undoing an increment​.

   decrement =: increment ^:_1

   decrement 5

4


Which led to defining subtraction which led to defining zero and negative
numbers. And so on for multiplication and division which then led to
rational numbers etc.


But I think anyone who had to suffer through redefining mathematics
formally would appreciate these uses of power.
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