Iteration Statements

CGS 3460, Lecture 17Feb 17, 2006Hen-I Yang

Previously… while statement do … while statement

Agenda

for statement Throw in the towel

For Statements

for (expr1; expr2; expr3) statement;

it’s the best when there’s a counting variable Gives programmer better control over the loop expr1: initialization expr2: condition (control loop termination) expr3: updates performed at the end of each

iteration

For Statements (II)

for (expr1; expr2; expr3) statement;

==

expr1;

while (expr2) {

statement

expr3;

}

For Statements (III) Omitting some expressions in for loop Infinite loop using for Comma Operator

Used only in for or macro Can be used in expr1 or expr3 Always have a side effect Lowest Precedence

Glue expressions to where there should only be one single expression

Not often used

Throw in the Towel

Break; Find it! Abort search User input causes stop Good for exiting in the middle Work on the innermost statement, only exits one level

Continue; Not interested. Skip the rest of the loop, and go directly to the next Remain inside the loop Continue can only be used for loop, not switch e.g. add 0 (from user’s input)

Throw in the Towel (II)

Goto: BAD BAD BAD idea

goto label;label: statement Bad habit from Basic Unstructured. Both break and continue are restricted, but not got

o Use goto to emulate break; Use goto for multi-level break? Spaghetti code (Hard to read, hard to modify)

return; exit();

to be discussed later

Null statement

; Empty loop body At the end of compound statement A line by itself to avoid confusion Putting ; after () in if, while or for will ends t

he statemen

Sample Code

. .. …. .. … .

Miscellaneous/Update

Homework 2 ClarificationEPA and fuel efficiency calculationHow to print strings/tags/message properly

using conversion specifications? Quiz 1 will be returned early next week

Average: around 73 Homework 1 hopefully will be returned late

next week

Summary

For statement Throw in the towel

Before you go

Read Chapter 6. Homework 2 due date countdown: D - 5