lecture7

# lecture7 - Wednesday, October 27 Function Re w vie...

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Wednesday, October 27 th Function Review Program Design and Decomposition Typecasting If we have some time, we’ll start ASCII This Friday's 2-4 section will meet in Botany 325 . The ACM will be showing you how to use the Visual Studio debugger ! Make sure to go! (The demo itself will start at about 3:15.)

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Function Review The foo function computes the average of two numbers and: 1. Returns the sum of the numbers. 1. 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 += n1; sum += n2; return(sum); avg = sum / 2; ] int main(void) { int mean, sum; sum = foo(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 += n1; return(sum); avg = sum / 2; ] int main(void) { int mean, sum; 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 6 3 6 (0+3+6)/3 3 1 3 1 1 3 6 1 (3+6+1)/3 3.3 Etc…
Reference Review void Silly(int byValue, int &byReference) { byValue = 10; byReference = 20; } void main() { int a = 5, b = 6; Silly(a,b); } When we pass a variable without using 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 void Silly(int byValue, int &byReference) { byValue = 10; byReference = 20; } void main() { int a = 5, b = 6; Silly(a,b); } When we pass a variable without using 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 6 byValue 5 byReference 10 20 Output: Reference Review What does it print?

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Programming Challenge void main(void) { int eyes, ears; cin >> eyes >> ears; switch (eyes + ears) { case 0: cout << “I think “; case 1: cout << “you are a goblin”; break; case 2: case 3: cout << “You ghoul ”; case 4: cout << “or a human”; break; default: cout << “not a ghost”; break; } } Convert the switch statement to the left into the equivalent set of if statements .
Top Down Design Today we’re going to learn how to attack large programming problems By breaking a big problem down into smaller, more manageable components, we make it easier to solve.

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## This note was uploaded on 11/07/2009 for the course CS 31 taught by Professor Melkanoff during the Spring '00 term at UCLA.

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lecture7 - Wednesday, October 27 Function Re w vie...

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