Empty string: Difference between revisions

Revision as of 16:17, 8 April 2023

Revision as of 15:00, 22 April 2023

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=={{anchor|nullable symbol}}Formal theory==

Formally, a string is a finite, ordered sequence of [[character (symbol)|characters]] such as letters, digits or spaces. The empty string is the special case where the sequence has [[length]] zero, so there are no symbols in the string.

There is only one empty string, because two strings are only different if they have different lengths or a different sequence of symbols.

In formal treatments,<ref>{{cite journal |first1=John |last1=Corcoran |first2=William |last2=Frank |first3=Michael |last3=Maloney |title=String theory |journal=Journal of Symbolic Logic |volume=39 |issue=4 |year=1974 |pages=625–637 |doi=10.2307/2272846 |jstor=2272846|s2cid=2168826 }}</ref> the empty string is denoted with '''[[ε]]''' or sometimes '''[[Λ]]''' or '''[[λ]]'''.