### Lifting Definition Option

René ThiemannArchive of Formal Proofs 2014.

### Abstract

We implemented a command that can be used to easily generate elements of a restricted type `{x :: ‘a. P x}`, provided the definition is of the form `f ys = (if check ys then Some(generate ys :: ‘a) else None)` where `ys` is a list of variables `y1` ... `yn` and `check ys ==> P(generate ys)` can be proved.

In principle, such a definition is also directly possible using the `lift_definition` command. However, then this definition will not be suitable for code-generation. To this end, we automated a more complex construction of Joachim Breitner which is amenable for code-generation, and where the test `check ys` will only be performed once. In the automation, one auxiliary type is created, and Isabelle’s lifting- and transfer-package is invoked several times.

### BibTeX

@article{RT-AFP14c, author = {René Thiemann}, title = {Lifting Definition Option}, journal = "Archive of Formal Proofs", month = oct, year = 2014, note = {\url{https://www.isa-afp.org/entries/Lifting_Definition_Option.html}, Formal proof development}, ISSN = {2150-914x}, }