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A rule-based program, performing lexical tokenization, is called tokenizer, [1] or scanner, although scanner is also a term for the first stage of a lexer. A lexer forms the first phase of a compiler frontend in processing. Analysis generally occurs in one pass.
The first edition (1986) is informally called the "red dragon book" to distinguish it from the second edition [5] and from Aho & Ullman's 1977 Principles of Compiler Design sometimes known as the "green dragon book". [5] Topics covered in the first edition include: Compiler structure; Lexical analysis (including regular expressions and finite ...
It is a computer program that generates lexical analyzers (also known as "scanners" or "lexers"). [ 3 ] [ 4 ] It is frequently used as the lex implementation together with Berkeley Yacc parser generator on BSD -derived operating systems (as both lex and yacc are part of POSIX ), [ 5 ] [ 6 ] [ 7 ] or together with GNU bison (a version of yacc ...
In more detail, in a compiler, the lexer performs one of the earliest stages of converting the source code to a program. It scans the text to extract meaningful tokens, such as words, numbers, and strings. The parser analyzes sequences of tokens attempting to match them to syntax rules representing language structures, such as loops and ...
Compiler analysis is the prerequisite for any compiler optimization, and they tightly work together. For example, dependence analysis is crucial for loop transformation. The scope of compiler analysis and optimizations vary greatly; their scope may range from operating within a basic block, to whole procedures, or even the whole program. There ...
Lex is a computer program that generates lexical analyzers ("scanners" or "lexers"). [1] [2] It is commonly used with the yacc parser generator and is the standard lexical analyzer generator on many Unix and Unix-like systems. An equivalent tool is specified as part of the POSIX standard. [3]
A parser generator generates the lexical-analyser portion of a compiler. It is a program that takes a description of a formal grammar of a specific programming language and produces a parser for that language. That parser can be used in a compiler for that specific language.
This stage of a multi-pass compiler is to remove irrelevant information from the source program that syntax analysis will not be able to use or interpret. Irrelevant information could include things like comments and white space. In addition to removing the irrelevant information, the lexical analysis determines the lexical tokens of the language.