Data - This too shall pass Thanks Dr. Mullins

1
Data - This too shall pass Thanks Dr. Mullins

• passing by reference may give back a
  value Chapter 4

2
Passing Data - by Value

• passing by valueA copy of a value is passed
  from the calling function to the called function.

Can use as temp vars
double Pythagorus(double a, double b) a
a a b b b double c sqrt(a
b) return c
double Pythagorus(double a, double
b) double c c sqrt(aa bb) return
c
9.0
16.0
3.0
4.0

3
Storing Values into Parameters
firstnum 865 secnum9090find_max(firstnum,
secnum)
find_max(x, y)
x
y
865
9090

4
Passing Data - by Value

• double Pythagorus(double, double)
• void main(void)
• double height 4.0, base 3.0
• cout ltlt Hypotenuse ltlt Pythagorus(height,
  base)ltltendl
• . . .
• double Pythagorus(double a, double b)
• double c c sqrt(aa bb)
• return c

5
Passing Data - by Value

• double Pythagorus(double a, double b)
• double c
• a
• b
• c sqrt(aa bb)
• return c

c
3.0
6.4
4.0
4.0
5.0
4.03.0
back in main cout ltlt height cout ltlt base

6
Passing Data by-value Example

• void print_val(int) // function prototype
• void main(void)
• int w 3
• cout ltlt"w before the function call is
  "ltltwltlt\n
• print_val(w)
• cout ltlt"w after the function call is
  "ltltwltlt\n
• void print_val(int q)
• coutltlt"Value passed to the function is
  "ltltqltltendl
• q q 2 // doubles the value
• coutltlt"Value at the end of the function is "ltlt q
  ltltendl

7
Passing Data by-value Results

• Output
• w before the function call 3
• Value passed to the function is 3
• Value at the end of the function is 6
• w after the function call is 3