Epigenetic regulation of transposable elements in the plant kingdom which allows for self-copying) within the coding of the transposon defines class I elements as autonomous or non-autonomous. Class I transposons can take the form of: Curiously, retrotransposons have been discovered to be the predominant form of transpositional element in plants with large genomes, such as maize and wheat, potentially indicating rapid success of this class of transposon in the creation of hybrids, such as wheat, peppermint and, in the distant past, maize. Plant hybridization often creates polyploids, with double, triple, quadruple or more the number of chromosomes present in the parent generation. Polyploid hybrids seem to be particularly susceptible
Quadruple-precision floating-point format the double-double technique above, although that technique does not implement IEEE quadruple precision), since direct hardware support for quadruple precision is, as of 2016, less common (see "Hardware support" below). One can use general arbitrary-precision arithmetic libraries to obtain quadruple (or higher) precision, but specialized quadruple-precision implementations may achieve higher performance. A separate question is the extent to which quadruple-precision types are directly incorporated into computer programming languages. Quadruple precision is specified in Fortran by the codice_2 (module codice_3 from Fortran 2008 must be used, the constant codice_4 is equal to 16 on most processors), or as codice_5, or in