Title
On the likelihood of normalisation in combinatory logic.
Abstract
We present a quantitative basis-independent analysis of combinatory logic. Using a general argument regarding plane binary trees with labelled leaves, we generalize the results of David et al. (see [11]) and Bendkowski et al. (see [6]) to all Turingcomplete combinator bases proving, inter alia, that asymptotically almost no combinator is strongly normalizing nor typeable. We exploit the structure of recently discovered normal-order reduction grammars (see [3]) showing that for each positive n, the set of SK-combinators reducing in n normal-order reduction steps has positive asymptotic density in the set of all combinators. Our approach is constructive, allowing us to systematically find new asymptotically significant fractions of the set of normalizing combinators. We show that the density of normalizing combinators cannot be less than 34%, improving the previously best lower bound of approximately 3% (see [6]). Finally, we present some super-computer experimental results, conjecturing that the density of the set of normalizing combinators is close to 85%.
Year
DOI
Venue
2017
10.1093/logcom/exx005
JOURNAL OF LOGIC AND COMPUTATION
Keywords
DocType
Volume
Combinatory logic,analytic combinatorics,normalization
Journal
27
Issue
ISSN
Citations 
7
0955-792X
0
PageRank 
References 
Authors
0.34
4
3
Name
Order
Citations
PageRank
Maciej Bendkowski1135.47
Katarzyna Grygiel2446.95
Marek Zaionc311117.27