SEMANTIC ANALYSIS

SEMANTIC ANALYSIS

1. Is a pass by a compiler that

   • Adds semantical information to the parse tree
   • Performs certain checks

2. Type

   • Theory
     • It provides the formal basis for design, analysis and study of type systems
     • It is use for
       • Constructing type checking algorithms
       • The theories of semantics of natural language
   • System
     • It defines how
       • a programming languague classifies values and expressions intro types
       • It can manipulate those types and their interaction
     • Functions
       • Safety
         • When a compiler detects meaningless or invalid code
       • Optimization
         • Static type checking that provides useful data to a compiler
       • Documentation
         • They illustrate the intent of the programmer
       • Abstraction
         • Types allow programmers to
           • Think about programs at a higher level
           • Express the interface between 2 systems
     • Class
       • Structural Type system
         • It determines if types are equivalent or if it is a subtype
         • Type compatibility and equivalence are determined by the type´s structure
       • Nominative system
         • Type compatibility and equivalence is determined by explicit declarations
   • Checking
     • Static type checking becomes a primary task of the semantic analysis
       • It is carried out by a compiler
     • Languagues
       • Typed languague
         • one data type cannot be performed on values of another type
       • Untyped languague
         • Any operation can be performed on any data type
     • Typing
       • Static
         • The meaningless operation will be detected when the program is compiled and rejected
           • C´s and Java´s
             • Require type declarations
               • Explicit
               • Implicit
       • Dynamic
         • The meaningless operation will be detected when the program is run resulting in a runtime exception
           • Duck Typing
             • A variable´s value itself implicitly determines what the variable can do
       • Strong
         • To describe how programming languages handle datatypes
       • Weak
         • Allows a value of one type to be treated as another
   • Inference
     • It is a feature present in some strongly statically typed programming languagues
     • Refers to the ability to automatically either partially or fully deduce the type of the value derivered
     • Algorithm
       • Hindley-Milner or Damas-Milner
   • Conversion
     • Changing an entity of one data type into another
       • Implicit
         • It is an automatic type conversion by the compiler
       • Explicit
         • Checked
         • Unchecked
         • Bit Pattern
   • Polomorphism
     • Ability of code to act on values of multiple types
     • Subtyping
       • There are subtypes to restrict the range of types that can be used in a particular case
     • Parametric
       • The code is written without mention of any specific type
     • Ad hoc
       • The range is finite and the combinations must be specified individually
       • Overloading
         • Kinds of ad hoc polymorphism
     • Advantages
       • Allows client programs to be written based only on the abstract interfaces of the objects
       • The future extensions in the form of new types of objects is easy