What is the role of a parser in a compiler?

A parser in a compiler checks the syntax of the source code and builds a data structure called a parse tree.

In more detail, a parser is a crucial component of a compiler, which is a program that translates source code written in a programming language into machine code that a computer can understand and execute. The parser's role is to ensure that the source code is syntactically correct, meaning it adheres to the rules and structure of the language in which it is written. If the source code does not follow these rules, the parser will generate an error message, and the compilation process will stop.

The parser operates after the lexical analysis phase of the compiler, which breaks down the source code into individual words or tokens. The parser takes these tokens and checks them against the grammar of the language. This grammar defines how tokens can be combined to form valid statements and expressions. If the tokens follow the grammar rules, the parser will construct a parse tree, a hierarchical data structure that represents the syntactic structure of the source code.

The parse tree is then used in the next stages of the compilation process, such as semantic analysis and code generation. The semantic analysis phase checks that the source code makes sense in the context of the language's semantics, while the code generation phase translates the parse tree into machine code.

A-Level Computer Science Tutor Summary: In simple terms, a parser in a compiler checks if the code you've written follows the correct language rules and structure, then creates a structure called a parse tree from it. This step is crucial because it ensures that the computer can understand and execute your code correctly. If there are mistakes in the code, the parser will stop the process and report errors.