# Lifting Definition Option

 Title: Lifting Definition Option Author: René Thiemann (rene /dot/ thiemann /at/ uibk /dot/ ac /dot/ at) Submission date: 2014-10-13 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{Lifting_Definition_Option-AFP, author = {René Thiemann}, title = {Lifting Definition Option}, journal = {Archive of Formal Proofs}, month = oct, year = 2014, note = {\url{http://isa-afp.org/entries/Lifting_Definition_Option.html}, Formal proof development}, ISSN = {2150-914x}, }``` License: GNU Lesser General Public License (LGPL)