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From `f`, we remove all "doubles" constructing a sequence
`f`': **N** -> **Q** that contains each positive rational number in
*exactly* one position.

Finally we can define an enumeration of *all* rationals

g:N->^{bijective}Qg(x) :=ifx= 0then0else ifxis eventhen-f'(x/2)elsef'((x-1)/2)

g= [0, 1, -1, 1/2, -1/2, 2/1, -2/1, 1/3, -1/3, 3/1, -3/1, ...].

Author: Wolfgang Schreiner

Last Modification: December 7, 1999