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. Preparation
Study chapter 7. This chapter is about expressions and assignments. See the
UML diagram.

.Image 08/ole.gif Expressions and Assignments

Answer review questions on chapter 7.

Hand in answers to 2 or more review questions.

. Note 1: Expressions are not Statements

Be careful to distinguish Expressions from Statements. Expressions are 
evaluated and return Values. Statements are executed and return a new 
State. Most languages have both.

. Note 2: Precedence and Associativity

You may want to express precedence and associativity in your project.

These are syntax not semantics. Express precedence and associativity in 
BNF/EBNF/XBNF not in the UML. It takes some extra definitions. See sections
3.3.1.7, 3.3.1.8 and 3.3.1.9 in the book.

For example, suppose we might define
   expression::= simple_expression #( operator simple_expression),
   operator::= "+" | "*".

But this does not show the relative precedence of "+" and "*".

We show the precedence of "*" and "+" in algebra by replacing the above by:
    expression::= term #( "+" term),
    term::= simple_expression #( "*" simple_expression).

To express associativity we can replace the '#' by recursion. For example:
    expression::= term | expression "+" term, -- left associative.
    term::= simple_expression| simple_expression "*" term, -- right 
associative.

Warning: it is unusual(and confusing) to have different associativities for
multiplication and addition in a real language.
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