Semantic Analysis dan Annotated Parse Tree | Teknik Kompilasi | Binus Online Learning

Summary

This presentation delves into the process of semantic analysis in program compilation. It explains how compilers check the meaning and context of instructions in source code, ensuring variable definitions, type consistency, and logical operations. The script covers key concepts like symbol validation, type checking, and how annotated parse trees are used to synthesize and inherit attributes. The discussion also includes practical examples, such as arithmetic expression parsing, to illustrate the importance of semantic checks in ensuring a program's correctness before it is compiled.

Takeaways

• 😀 Semantic analysis helps determine the meaning of instructions in a source program after scanning and parsing.
• 😀 The first step in semantic analysis is separating the instructions in the program and identifying known functions.
• 😀 Semantic analysis checks the validity of function names and the consistency of types across operations in the program.
• 😀 Symbol checking ensures that variables and functions are defined before they are used in the program.
• 😀 Type checking verifies that the data types used in operations are compatible (e.g., adding integers or multiplying floats).
• 😀 Semantic analysis occurs after scanning and parsing, focusing on the global structure and correctness of the program.
• 😀 Annotated parse trees are used to attach semantic information (like values or types) to nodes, which helps in understanding the program’s behavior.
• 😀 Synthesized attributes are calculated from child nodes in the parse tree and passed upwards (e.g., type information).
• 😀 Inherited attributes are passed down or across parent and sibling nodes in the parse tree, typically affecting the result of operations.
• 😀 The semantic analysis process ensures logical consistency in the program, making sure that the code is not just syntactically correct but also semantically valid.
• 😀 The importance of grammar definitions: when analyzing a program, semantic actions depend on correct grammar rules to process and check attributes correctly.

Q & A

What is the primary function of semantic analysis in the compilation process?

Semantic analysis is used to determine the meaning of a series of instructions in a source program. It ensures that the program is logically correct, checking for issues like type mismatches and undefined variables.

What role does the compiler play in semantic analysis?

The compiler checks whether the functions and variables in the program are defined correctly and whether their usage matches the expected types. It also verifies that there are no semantic errors, such as undeclared variables or invalid operations.

What is the difference between semantic analysis and syntactic analysis?

Syntactic analysis focuses on the structure of the code, ensuring it follows grammar rules, while semantic analysis checks the meaning behind the code, such as verifying that operations between variables make sense and that variables are properly defined.

How does semantic analysis handle type checking?

Semantic analysis ensures that operands in expressions have compatible types for the operations being performed. For instance, if an addition operation is performed between two variables, their types must be compatible, like adding two integers.

What is an annotated parse tree, and why is it important in semantic analysis?

An annotated parse tree is a tree structure that represents the syntax of a program, with additional semantic information added to the nodes. This helps track the values and types of variables, ensuring that the program is semantically valid as it is parsed.

What are inherited and synthesized attributes in the context of semantic analysis?

Inherited attributes are values passed down from a parent node to a child node in the parse tree, while synthesized attributes are computed from the child nodes and passed up to the parent node. These attributes help determine things like variable types and the results of expressions.

Can you provide an example of how attribute computation works in semantic analysis?

In the example expression `4 * 5 + 6`, the lexical values (4, 5, and 6) are first assigned to the leaf nodes. The result of `4 * 5` is computed, and then `6` is added to it, giving the final result of `26` through the use of synthesized attributes.

What is the purpose of checking name validity during semantic analysis?

Checking name validity ensures that all variables and functions used in the program are properly defined and do not conflict with other identifiers. It verifies that names are not redefined within the same scope or used before they are declared.

What happens if a semantic error is found during the analysis process?

If a semantic error is found, the compiler will typically generate an error message indicating the issue, such as an undefined variable or a type mismatch, preventing the program from compiling successfully until the error is resolved.

How does semantic analysis differ from lexical analysis and parsing?

Lexical analysis breaks down the program into tokens, and parsing organizes these tokens into a syntactic structure. Semantic analysis, however, goes beyond the structure to verify the logical consistency and correctness of the program's instructions.