kn1kn12n2

kn1kn12n2 is a compact token used in theoretical computer science to illustrate patterns in lexical analysis. It is defined as the concatenation of three sub-tokens: kn1, kn12, and n2. As a simple, well-formed string, it is commonly employed in formal language and compiler design exercises to demonstrate how different tokenization schemes handle overlapping prefixes.

The complete string consists of nine characters: k, n, 1, k, n, 1, 2, n, 2. It can be decomposed as kn1 + kn12 + n2, where kn1 is the characters 'k','n','1'; kn12 is 'k','n','1','2'; and n2 is 'n','2'. This decomposition aligns with a maximal-munch tokenization under a token set that includes kn1, kn12, and n2.

Under the fixed token set {kn1, kn12, n2}, the canonical tokenization is [kn1] [kn12] [n2]. If a different lexicon is used, such as separate single-character tokens, the same string could be split into [k][n][1][k][n][1][2][n][2], illustrating how token definitions influence parsing decisions. The example thus highlights the importance of consistent token definitions in compiler design.

Variants like kn1kn11n2 or kn2kn12n3 modify the numeric suffixes to create alternate token boundaries, commonly used to test the extensibility and disambiguation of a given tokenizer. In teaching materials, kn1kn12n2 often serves as a familiar, constraint-rich fixture for illustrating deterministic versus non-deterministic lexing choices.

See also: lexical analysis, tokenization, formal language, regular expressions, tokenizer, compilers.