tokeniser

A tokeniser, also known as a lexical analyser or scanner, is a fundamental component in computer science, particularly in the fields of compilers and natural language processing. Its primary function is to break down a stream of characters, typically source code or text, into smaller, meaningful units called tokens. These tokens represent the basic building blocks of the input and are essential for subsequent processing stages.

In the context of programming languages, a tokeniser identifies elements such as keywords (e.g., `if`, `while`), identifiers (variable names), operators (`+`, `-`, `=`), literals (numbers, strings), and punctuation marks (`;`, `,`). For example, the C code `int x = 10;` might be tokenised into `INT`, `IDENTIFIER(x)`, `OPERATOR(=)`, `INTEGER_LITERAL(10)`, and `SEMICOLON`. The specific set of tokens and the rules for their recognition are defined by the grammar of the programming language or the structure of the text being processed.

In natural language processing, tokenisation involves splitting text into words, punctuation marks, or other significant elements. This process can be more complex due to variations in language, such as contractions (e.g., "don't" becoming "do" and "n't"), hyphenated words, and different forms of punctuation. The output of a tokeniser serves as the input for parsers, which further analyse the structure and meaning of the tokens.