Compiler lecture 06
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The document discusses the syntax analyzer phase of compiler construction. The syntax analyzer checks the syntactic structure and context-free grammar of a program after lexical analysis. It uses a parser to analyze the token stream from the lexical analyzer against production rules to detect errors and generate a parse tree representing the syntactic structure of the input. The parse tree shows how grammar rules were applied and is used to define the syntax structure.
Compiler lecture 06
- 1. Compiler Construction By Noor wali Khan UOCH
- 2. Syntax Analyzer • Syntax analysis is a second phase of the compiler design process that comes after lexical analysis. • It analyses the syntactical structure of the given input. • The syntax analyzer also checks whether a given program fulfills the rules implied by a context-free grammar. • We have seen that a lexical analyzer can identify tokens with the help of regular expressions and pattern rules.
- 3. Syntax Analyzer • But a lexical analyzer cannot check the syntax of a given sentence due to the limitations of the regular expressions. • Regular expressions cannot check balancing tokens, such as parenthesis. • Therefore, this phase uses context-free grammar (CFG), which is recognized by push-down automata. • CFG, on the other hand, is a superset of Regular Grammar, as depicted below: Regular Grammar CFG
- 4. • It implies that every Regular Grammar is also context-free, but there exists some problems, which are beyond the scope of Regular Grammar. • CFG is a helpful tool in describing the syntax of programming languages.
- 5. Syntax Analyzer •A syntax analyzer or parser takes the input from a lexical analyzer in the form of token streams. •The parser analyzes the source code (token stream) against the production rules to detect any errors in the code. The output of this phase is a parse tree.
- 7. Parse Tree • It is a generalized type of tree which shows pictorially that how grammar rules are applied on the sequence of character. • Parse tree is the output of the syntax analyzer and is used for designing/defining syntax structure. • The parse tree describes the syntactic structure of the input.
- 8. Syntax Tree • Compressed form of parse tree which contains operators as internal node and operands of the operator to be the children of its internal node. = Id + Id * Id num