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| Title: | On Two Letters versus Three |
| Authors: | Kozen, Dexter |
| Keywords: | computer science
technical report |
| Issue Date: | 4-Feb-2002 |
| Publisher: | Cornell University |
| Citation: | http://techreports.library.cornell.edu:8081/Dienst/UI/1.0/Display/cul.cs/TR2002-1860 |
| Abstract: | If A is a context-free language over a two-letter alphabet, then the set of all words obtained by sorting words in A and the set of all permutations of words in A are context-free. This is false over alphabets of three or more letters. Thus these problems illustrate a difference in behavior between two- and three-letter alphabets. |
| URI: | http://hdl.handle.net/1813/5845 |
| Appears in Collections: | Computer Science Technical Reports
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