1. CS1010 Discussion Group 11
Week 5 – Functions, Selection, Repetition

2. Slides are at http://www.comp.nus.edu.sg/~yanhwa/
HELLO!
Slides are at

3. Have you submitted your Lab #2?Do
Read qn carefully, plan
Give meaningful names for variables (no t1, t2, a, b, c…)
Appropriate commenting
Need to use functions
Add spaces, empty lines appropriately
Balance the number of vars created
Must do
Double/triple check your indentation (gg=G in vim will auto-indent your program nicely!)
Add function description, preconditions and postconditions (if any)
Do not
Add function description elsewhere other than on the top of the function
Follow lab guidelines

4. Some tips If else Shorthand notation (Ternary Logic)
return (answer1 > answer2 ? answer1 : answer2);
Padding of zeros
printf("%06d", zipCode);

5. .bashrc and .vimrc

6. Number, order, type of parameters Function description
Lecture Summary
Functions recap
Function prototypes
Parameter names may be omitted in the prototype, but not their type
Number, order, type of parameters
Function description
Precondition, postcondition
A function should perform either computation or I/O, not both.

7. Lecture Summary
warning: implicit declaration of function 'f‘
warning: conflicting types for 'f'
1 #include <stdio.h> 2
3 int main(void) {
4 f(100, 7);
5 return 0;
6 } 7
8 void f(int a, int b) {
9 return a*b*b;
10 }
Why will this happen?
Without function prototype, compiler assumes function f to be an int function when it encounters f(100, 7); in main(). But it later conflicts with void f()
A ‘type-less’ function has default return type of int

8. Lecture Summary
What is pass-by-value?

9. Short-circuit evaluation (if A && B) (if A || B)
Lecture Summary
(5<2) + (6==5)
A && B
A || B !A
== vs =
Short-circuit evaluation (if A && B) (if A || B)
Boolean flags “is…” “has…”
Switch statement

10. Switch statement Lecture Summary
switch ( <variable or expression> ) {
case value1:
Code to execute if <variable or expr> == value1
break;
case value2:
Code to execute if <variable or expr> == value2
case value3:
Code to execute if <variable or expr> == value3
...
default:
Code to execute if <variable or expr> does not
equal to the value of any of the cases above }

11. Lab
CodeCrunch Lab #2
Have you submitted?

12. while ( condition ) { // loop body } Repeat if a condition is true
Lecture Summary
Repeat if a condition is true
while ( condition ) {
// loop body }

13. Repeat for a certain number of times
Lecture Summary
Repeat for a certain number of times
Steps:
n=1;
if (n<=10) { printf(…); n++; Go to step 2 }
Exit the loop
int n;
for (n=1; n<=10; n++) {
printf("%3d", n); }
Same as “for n  1 to 10 STEP 1”

14. Square-free integer? What’s that?
Lab
CodeCrunch Lab #3
Square-free integer? What’s that?

15. Tutorial 3 Q1a
The expression is evaluated from left to right: (0 < value), being a relational operation (also called comparison operation), evaluates to True when value = 0.5
The hint will print out 1 because the return value for true is 1 in C

16. Exploration
What is a string? %s
What is a char? %c
max = ?

17. Tutorial 3 Q6
#define FEMALE 0
#define MALE 1
#define ACCEPTABLE 0 ….
int body_type(int gender, double wt, double ht) {

18. Tutorial 2 Q7
Modularity: Reuse of codes, top-down design, ease of debugging, ease of editing function without affecting other parts of the program
Do not mix input/output with computation

19. Tutorial 2 Q9
Confusing local scope:

20. Functions and call stack https://www.youtube.com/watch?v=jRcll9qY6b 0
Functions call stack
Functions and call stack 0

21. What are functions and why they are useful
Summary
What are functions and why they are useful
Local scope of variables in functions
Function prototype, description, precond
Selection statements (if-else, boolean true false, switch statements). Neat logic!!
Repetition (will be covered more next week)