Expression and Assignment

BAB V

Expression and Assignment Statement

Arithmetic Expression

Operators

·         Unary, one operand

·         Binary, two operands

·         Ternary, three operands

Operator Precedence Rules

1.       Parentheses

2.       Unary operator

3.       *, /

4.       +, -

Associativity Rules, The operator associativity rules for expression evaluation define the order in which adjacent operators with the same precedence level are evaluated

Conditional Expression (IF statement)

Example

·         average = (count == 0)? 0 : sum / count

·         if (count==0)

{

                Average=0;

}

Else

{

                Average=sum/count;

}

Operand evaluation order

1.       Variables: fetch the value from memory

2.       Constants: sometimes a fetch from memory; sometimes the constant is in the machine language instruction

3.       Parenthesized expressions: evaluate all operands and operators first

4.       The most interesting case is when an operand is a function call

Overloaded Operators

Use of an operator for more than one purpose is called operator overloading

e.g. + for integer and float, 6 + 9.50.

A narrowing conversion is one that converts an object to a type that cannot include all of the values of the original type e.g., float to integer.

A widening conversion is one in which an object is converted to a type that can include at least approximations to all of the values of the original type e.g., integer to float.

Explicit type conversions

Called casting in C-based languages

Examples

C : (int)angle

Implicit type conversions

double F=9.4;

int Z=F;

Z will have a value of 9 rather than 9.4;

Relational Expressions are (!=, /=, ~=, .NE., <>, #)

Short Circuit Evaluation

An expression in which the result is determined without evaluating all of the operands and/or operators

Example: (13 * a) * (b / 13 – 1)

If a is zero, there is no need to evaluate (b  /13 - 1)