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# lecture7%2Dpost - Wednesday, October 27 FunctionReview

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Wednesday, October 27 th Function Review Program Design and Decomposition Typecasting If we have some time, we’ll start  ASCII

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Function Review The  foo  function computes the  average of two numbers and: 1. Returns  the sum of the numbers. 2. Sends back the average of the  numbers in the  third reference  parameter . Whats  wrong  with it? VOID foo(int n1, n2, int avg) ( int sum; sum += num1; sum += num2; return(sum);    avg = sum / 2; ] int main(void) { int mean, sum; sum = func(5,9,mean); cout << sum << “ “ << mean; } { = 0; avg = sum / 2; return(sum); } int foo(int n1, n2, int avg) int foo(int n1, int n2, int avg) int foo(int n1, int n2, int avg) VOID foo(int n1, n2, int avg) ( int sum; sum += num1; sum += num2; return(sum);    avg = sum / 2; ] int main(void) { int mean, sum; sum = func(5,9,mean); cout << sum << “ “ << mean; }
Function Review What does the  following program print  out? What is the value of  credit after lines  1 2   and  3  have executed. float credit; void charge(float amount) { if (amount <= credit) { cout << “Approved.\n”; credit -= amount; } else cout << “Rejected!\n”; } int main(void) { credit = 100.00; // starting charge(52); // line 1 charge(10); // line 2 charge(40); // line 3 }

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Function + Static Review float moving_avg(float cur) // avg of last 3 { static float s1,s2,s3; s1=s2; s2=s3; s3=cur; return((s1+s2+s3)/3); } int main(void) { float avg; avg=moving_avg(3); cout << avg << “\n”; avg=moving_avg(6); cout << avg << “\n”; avg=moving_avg(1); cout << avg << “\n”; avg=moving_avg(2); cout << avg << “\n”; } What does it print? s1 0 s2 0 s3 0 avg 3 cur 3  3 (0+0+3)/3 1 6 cur 6  3  6 (0+3+6)/3 3  1  3 1 cur 1  3  6  1 (3+6+1)/3 3.3 3.3 Etc…
Reference Review { byValue = 10; byReference = 20; } void main() { int a = 5, b = 6; Silly(a,b); cout << a << “ “ << b; } When we pass a variable without using  a reference,  it is called  passing by value . When we pass a variable using a reference, it is called  passing by reference . When we pass by value,  the program makes a  copy  of the actual  parameter and sends it  to the function.

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Reference Review { byValue = 10; byReference = 20; } void main() { int a = 5, b = 6; Silly(a,b); cout << a << “ “ << b; } When we pass a variable without using  a reference,  it is called  passing by value . When we pass a variable using a reference, it is called  passing by reference . When we pass by  reference , the program  references the actual  parameter in the calling  function.
void Silly(int byValue, int byReference) { byValue = 10; byReference = 20; } void main() { int a = 5, b = 6; Silly(a,b); cout << a << “ “ << b; }                  a    5                           b

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## This note was uploaded on 04/10/2012 for the course CS 31 taught by Professor Melkanoff during the Winter '00 term at UCLA.

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lecture7%2Dpost - Wednesday, October 27 FunctionReview

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