Compiler Design

Chomsky Hiearchy

- All Grammars - Context Sensitive - Context Free - Regular

Identifying Keywords

- Create Transition Diagrams for each word - Install reserved words initially in the symbol table

Analysis

- Lexical - Syntax - Semantic

Synthesis

- Target Code Generation - Target Code Optimisation

LL(K) Grammars

- eliminate ambiguities - eliminates left recursion - performs left factoring

Syntax Directed Definitions

A CFG where: - Grammar symbols are a set of attributes - Production rulles have an associated set of semantic rules for computing attribute values

Dependency Graph

A directed Graph G - (N,E) - includes nodes for each attribute in the tree - a directed edge exists between two vertices when you need X.c to compute A.b

Symbol Table

A mapping from a name to what it refers to. It's used during the analysis phase. You continuously scope the symbol table with information about what is in the scope.

Compiler

A program that transforms a program in one language to an equivalent program in another language.

Semantic Analysis

Checks semantic consistency

Syntax Analysis

Creates the syntax tree

Left Factoring

Defer prefix decisions until later. A -> aB, bB, cB.. xB becomes A -> UB U -> a|b|c|d|..

Interpreter

Directly executes the operations specified in the source, specified by inputs supplied by the user.

Disambiguating Rules

Impose precedence of certain rules. (i.e: * is greater than +).

Lexical Analysis

Reads the character streams

Top Down Parsing

Recursive Descent Parsing. The tree is constructed Top-Down, Left-Right.

Predictive Parsing

Recursive Descent with some predictions. - No backtracking!

Synthesis

Target Code Generation

Left Recursion

This is when for some non-terminal A and some string a, A^+ => Aa.

Synthesized

Value is determined by children and itself - evaluate in some bottom up order

Inherited

Value is determined by parents, siblings, and itself. - evaluate in some top down order

Ambiguous Grammars

When there exists more than one parse tree for the same string. You will need additional rules to make it clearer.