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

2. 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 S. Tanimoto Syntax

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

4. 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 S. Tanimoto Syntax

5. 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 S. Tanimoto Syntax

6. 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 / F
25 / total
CSE S. Tanimoto Syntax

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