W.B.Langdon . 7 Oct 2022 2017 papers , full list
William B. Langdon, Dept of Computer Science, University College London, Technical Report 10157010, 25 August 2022, UCL Discovery. doi:10.14324/000.rp.10157010 PDF
We use the recent random_tree() addition to GPquick [arXiv:2001.04505] to uniformly sample in linear time the space of binary trees. A unix gawk script transforms these to uniform random infix expressions, as used by Free Software Foundation GNU core utility expr. It converts from Lisp s-expression like prefix representation used by GPquick to bracketed infix expressions, e.g. "(" 3050 "=" 5514 ")" "-" 3073. gawk randomly labels internal tree nodes with the 14 functions known to expr and replaces leafs with randomly chosen positive integers up to 32768. About 80 percent of random expressions are rejected, since they cause expr to fail, typically due to division by zero.