ModularWord

The unique positive word in and of a matrix in with non-negative entries — which is also its path down the Stern–Brocot tree.

WikipediaModular groupMathWorldModularGroupGammaWikidataQ1834342

ModularWord(matrix)the positive word

ModularMatrix(a, b, c, d)a matrix; every head here also accepts the word in its place

ModularSTWord(matrix)the alternating / factorisation, as its list of -exponents

Domain: The modular group

Details

and generate the positive cone
The peel never searches: comes off when and , when and , and both at once would force determinant
`ModularKind` sorts by against — elliptic, parabolic, hyperbolic
A positive word is hyperbolic exactly when it uses both letters; all- and all- are parabolic
Rebuilding from an / word can return : that sign is the that quotients out

Examples

See also: ContinuedFraction, ModularClasses, RademacherSymbol