You might have read (about) the book Domain-Specific Languages written by Martin Fowler. As the name suggests it is about these little useful programming languages you can built very easily with Xtext.
A better approach is to parse the XSLT stylesheet into memory once, compile it to machine-format, and then preserve that machine representation in memory for repeated use. This is called stylesheet compilation and is no different in concept than the compilation of any programming language.
When John McCarthy in 1960 wrote his famous paper on the programming language LISP, he used a particular function to illustrate what you could do with the
Demonstrates how you can use animated updates to open and close sections of a table view for viewing, where each section represents a play, and each row contains a quotation from the play. It also uses gesture recognizers to respond to user input: * A UITapGestureRecognizer to allow tapping on the section headers to expand the section; * A UIPinchGestureRecognizer to allow dynamic changes to the height of table view rows; and * A UILongPressGestureRecognizer to allow press-and-hold on table view cells to initiate an email of the quotation.