Midterm -- Reminder July 2 -- Thru Ch. 7

• Practice by doing problems at the end of chapters...self-test exercises at the end of each section.

Project 2 due, this week... June 28
 

Looping

• while(expression)

  statement

Looping

• while(expression)

  statement
• Reading the statement:

  while expression is true, do statement

Looping

• while(expression)

  statement
• Breaking apart the loop:

  test (expression == true) ->
  execute statement -> go back to test.

Looping

• do statement while(expression);

Looping

• do statement while(expression);
• Reading the statement:

  do statement until expression is false

Looping

• do statement while(expression);
• Breaking apart the loop:

  execute statement ->
  test (expression == true) ->
  go back to execute statement

Looping

What's the difference?

• while(expression)

  statement
• do statement while(expression);

Looping

What's the difference?

• while(expression)

  statement
• test before execution
• do statement while(expression);
• test after execution

Looping

• for(initialization; expression; update)

  statement

Looping

• for(initialization; expression; update)

  statement
• Initialization:  Any statement...
• used to initialize variables used in the loop.

Looping

• for(initialization; expression; update)

  statement
• expression is the same as for a while loop.

Looping

• for(initialization; expression; update)

  statement
• statement is executed next!

Looping

• for(initialization; expression; update)

  statement
• update is used to update variables used in the loop.
• executed last, right before test

Looping

• for(initialization; expression; update)

  statement

execute initialization ->
test (expression == true) ->
execute statement -> execute update -> go back to test (expression == true)

Looping

• for(initialization; expression; update)

  statement

any for loop can be written as a while...and vice versa

Looping

Writing loops as different types...

• for(initialization; expression; update)

  statement
 
• initialization;

while (expression) {
  statement;
  update;
}

Looping

Writing loops as different types...

• Why one type of loop over another?
• while loops
• do...while loops
• for loops

 

Looping

Writing loops as different types...

• Why one type of loop over another?
• for loops
• used for situations where you update something, and then check the condition. (incrementing....)

 

Looping

Writing loops as different types...

• Why one type of loop over another?
• do...while loops
• When you have to do something before you check the condition the first time (such as getting a password, where you have to get the password the first time, before you check whether the password is correct...)

Looping

Writing loops as different types...

• Why one type of loop over another?
• while loops
• catchall for the rest... whenever a for loop is not natural, but do...while is not necessary.

 

Looping

Writing loops as different types...

• Why be able to write loops as different types of loops?
• Sometimes you may have to change what type of loop is there because it is no longer natural... instead of using arrays (a natural for loop situation), you begin using linked lists, or files...

 

Looping

Directing flow of control

• break
• continue
• goto

Looping

Directing flow of control

• break
• gets out of the current loop immediately!
• NOTHING else done before loop exit...  like a 'mini'-return.
• only exits the current loop it is in...  see nesting.

Looping

Directing flow of control

• continue
• go to the test statement, skip the rest of the loop.
• sometimes you don't want to execute the entire loop...

Looping

Directing flow of control

• nesting, and goto
• sometimes, you have to have loops within loops
• break only gets out of ONE loop (block).
• goto goes directly to label.
• goto label;

Looping

Directing flow of control

• nesting, and goto
• while (fin >> ch) {

  for (int i = 0; i < 5; i++) {
    if (ch == '\n') break;
    if (ch == ' ') continue;
    if (ch == EOF) goto abnormalTermination;
    ch += 15;
  }
}
abnormalTermination:
  return 0;