+ - * ÷ two numbers in
3.14 decimal notation,
1RLLRRLLRRLLRR stern–brocot notation, or
[1;1,2,1] something close to continued fraction notation
Milad Niqui: Exact arithmetic on the Stern-Brocot tree. https://core.ac.uk/download/pdf/82481132.pdf
HAKMEM p. 40 - ITEM 101B (Gosper): Continued Fraction Arithmetics https://w3.pppl.gov/~hammett/work/2009/AIM-239-ocr.pdf