Tokenization: The primary task of a lexical analyzer is to divide the source code into meaningful units called tokens. Tokens are the smallest meaningful units of a programming language, such as keywords, identifiers, constants, operators, and punctuation symbols. The lexical analyzer identifies these tokens based on predefined patterns or rules specified by the language's grammar.
Skipping Irrelevant Characters: The lexical analyzer skips irrelevant characters, such as white spaces, comments, and formatting elements, that do not contribute to the program's meaning. These characters are typically removed to simplify subsequent phases of the compilation process.
Lexical Error Detection: Another critical role of the lexical analyzer is to detect and handle lexical errors in the source code. Lexical errors occur when the input does not conform to the lexical rules of the programming language. Examples of lexical errors include misspelled identifiers, unrecognized symbols, or malformed constants. The lexer can raise an error or provide error recovery strategies to handle these situations gracefully.
Symbol Table Management: In addition to tokenization, a lexical analyzer often manages a symbol table. A symbol table is a data structure that stores information about identifiers (variables, functions, classes) encountered during lexical analysis. It records their names, data types, scope information, and other relevant details. The symbol table is typically used by subsequent compiler phases, such as the parser and the semantic analyzer, to perform name resolution and type checking.
Efficiency Optimization: A well-designed lexical analyzer employs various techniques to optimize its performance. These techniques may include buffering input characters, implementing state machines or finite automata, using efficient data structures for token representation, and minimizing unnecessary operations to improve overall scanning speed.
Integration with Parser: The output of the lexical analyzer, the stream of tokens, is typically fed into the parser, which constructs the program's syntax tree. The parser relies on the lexer to provide a steady stream of tokens according to the programming language's grammar. The lexer communicates with the parser, usually through a token interface, to deliver tokens on demand.
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