1. Arithmetic Expressions Function Calls Output
Chapter 3

2. Coming Up Next Understanding and evaluating expressions.
Formatting output
Calling functions and using parameters

3. Precedence Rules Expressions are made up of
variables
operators
parentheses
Precedence similar to algebraic precedence
Highest is ( )
* / %
Mult division mod (remainder)
Addn subt

4. Precedence Rules
What is the output of this program ?
Integer Division

5. Type Coercion
Integer values stored differently in memory than float values
Variables declared as float can hold only float values
This would “coerce” the program to change 5 to 5.0 and store it in num
Happens implicitly

6. Type Casting
Sometimes you wish to explicitly force the program to convert from one type to another
Use the name of the type as if it is a function

7. Mixed Type Expressions
When operands are of different data types
Results in (implicit) type coercion
What are the types of these expressions?

8. Function Calls & Library Functions
A function is called (invoked) by using its name
as a statement or command
as a value (to be printed, assigned, etc.)

9. Function Calls and Library Functions
All functions have a parameter list
The list may be empty, but the parentheses must be included in the call

10. Functions -- Two Versions
Value returning function
called as if it is a value
needs a return statement
Function to do a task
a void function
called as if it is a statement

11. Value Returning Functions
Function call is used as a value (as in an expression)
Do not use as a separate statement
The function computes a value (or result)
The function returns exactly one result
A function written by a programmer should not to tasks (such as I/O)

12. Library Functions A standard library of often used functions exists
See partial listing, pg 66 of text
See Appendix C, pg A2 for larger listing

13. Library Functions
What do the following functions do? Value returning or void?
exp(x)
atof(str)
strcpy(dest, source)
tolower(ch)
isdigit (ch)

14. Void Functions When declared, type is void
A function that does not return a value
return statement will be a syntax error
It’s purpose is to do a task
Called a procedure or subroutine in some languages
Invoked or called as a statement
not as a value

15. Formatting the Output Normally cout will just jam values together
uses scientific notation for float values
We need formatting capabilities
include blanks (blank lines, blank spaces)
right and left justify output in a specified number of columns
specify fieldwidth, precision for float output

16. Creating Blank Lines cout << “whatever” << endl;
Stands for “end Line”
Sends a “carriage return” and “line feed”
Caused paper roller to advance (rotate) one line
Sent the typing head to the left margin

17. Inserting Blanks Within a Line
Used to separate output values
Include character space or string of spaces

18. Manipulators We have used endl as a “manipulator”
Behaves like a function
causes an action to occur
Looks like a data object
appears in midst of insertion << operations

19. Manipulators To right justify output in specified number of spaces
To specify number of decimal digits to be output
Note required include and cout.setf
Note rounding

20. Style -- Program Formatting
Header with /* comments */ about the program
Required documentation
// comments for clarification of identifiers
// comments with descriptions of program sections
Use white space, indenting

21. Testing and Debugging Hints
Check precedence in expressions
Explicit type casts make program more clear
Both sides of assignment statements should be same type
Library functions require correct #include statement
Functions need correct number and order for parameter lists