CSE 341 -- S. Tanimoto Syntax Syntax vs Semantics Backus-Naur Form Extended BNF Derivations Parse Trees CSE 341 -- S. Tanimoto Syntax

CSE 341 -- S. Tanimoto Syntax Syntax: The grammatical form of programs. vs Semantics: The meaning of the program Syntax (of textual languages) is typically specified by production rules for a context-free grammar using Backus-Naur Form (BNF) or Extended BNF (EBNF) In visual languages, syntax is described by a set of restrictions on how diagrams may be constructed. (e.g., connection constraints) CSE 341 -- S. Tanimoto Syntax

CSE 341 -- S. Tanimoto Syntax Syntactic Components Identifiers and reserved words Numeric constants Parentheses, braces and brackets Expressions Statements CSE 341 -- S. Tanimoto Syntax

BNF (Backus-Naur Form) (2.0 * PI) / n <expression> ::= <expression> + <term> | <expression> - <term> | <term> <term> ::= <term> * <factor> | <term> / <factor> | <factor> <factor> ::= number | name | ( <expression> ) CSE 341 -- S. Tanimoto Syntax

CSE 341 -- S. Tanimoto Syntax Extended BNF Optional constructs written as [ x ] Zero or more of x written as { x } Choice (“or”) written using | Grouping with parentheses ( x | y ) as in { (x | y ) z } <expression> ::= <term> { (+ | -) <term> } <term> ::= <factor> { (* | /) <factor> } <factor> ::= ’(’ <expression> ’)’ | name | number CSE 341 -- S. Tanimoto Syntax

CSE 341 -- S. Tanimoto Syntax Derivation E ::= E + T | E - T | T T ::= T * F | T / F | F F ::= number | name | ( E ) E E + T T + T T / F + T F / F + T F / F + F 25 / F + F 25 / 100 + F 25 / 100 + total CSE 341 -- S. Tanimoto Syntax

CSE 341 -- S. Tanimoto Syntax Parse Trees E ::= E + T | E - T | T T ::= T * F | T / F | F F ::= number | name | ( E ) 25 / 100 + total number / number + name F F F T T T E E CSE 341 -- S. Tanimoto Syntax