Class 3: Rules of Evaluation

Assignments Due

• Monday, 5 September (11:01am): Problem Set 1 (both on-line submission and paper)
• Wednesday, 7 September (in class): Quiz 1

Reading

• Now: should have finished Chapters 1-3 of the course book
• By Friday: Chapter 4 of course book, Chapters 1-3 of James Gleick’s The Information

Upcoming Help Schedule

• Right after class today (Monday, noon-1:30pm): Kristina, Rice Hall, first floor
• Monday, 1-2pm: Dave, Rice 507 (almost last chance to pick up a book)
• Tuesday, 5-8pm: Jonathan, Valerie, Rice Hall, first floor

BNF Scheme Grammar with Rules of Evaluation

Expression ::= PrimitiveExpression

PrimitiveExpression ::= Number | true | false | Primitive Procedure

Evaluation Rule 1: Primitives. A primitive, evaluates to __________________________________________.

Expression ::= NameExpression

NameExpression ::= Name

Evaluation Rule 2: Names. A name expression evaluates to __________________________________________.

Expression ::= ApplicationExpression

ApplicationExpression ::= (Expression MoreExpressions)


MoreExpressions ::=


MoreExpressions ::= Expression MoreExpressions

Evaluation Rule 3: Application. To evaluate an application:
    (a) Evaluate all the subexpressions (in any order)
    (b) Apply the value of the first subexpression to the values of all the other subexpressions.

Application Rule 1: Primitives. If the procedure to apply is a primitive, __________________.

Application Rule 2: Constructed Procedures. If the procedure is a constructed procedure, ___________________ the body of the procedure with each formal parameter replaced by the corresponding actual argument expression value.