COMP102

1
COMP102 Programming Fundamentals I

• LA2B (Mon 5-7pm)
• LA2E (Fri 3-5pm)
• LA2F (Fri 5-7pm)
• TA Jackie Lo

2
Lecture Review

• More on Array
• CANNOT copy all elements of one array into
  another with an assignment statement
• array2 array1
• Must use a loop instead
• for (int i0 iltarray_size i)
• array2i array1i

3
Lecture Review

• Passing Arrays to Functions
• Passing array as parameter pass by reference
• NO sign
• To ensure no modification inside function
• i.e. all elements in the array are read-only
• Add a const modifier before the array parameter
• double func(const int array)

4
Lecture Review

• Declare functions with array as parameter
• 1-D
• int func (int array, int row)
• int func (int arrayltconstant row sizegt)
• 2-D
• int func (int arrayltconst col sizegt, int
  row)
• int func (int arrayltconst row sizegtltconst col
  sizegt)
• E.g.
• int func1(int a) // invalid!
• int func2(int a3) // valid!

5
Lecture Review
void fun1(int a) void main() int
lab_score1035 fun1(lab_score01)

• More E.g.

void fun1(int a) void main() int
midterm35 fun1(midterm)
void fun1(int lab_score10) void main()
int lab_score3510 fun1(lab_score)
6
Lecture Review

• More on Char array
• String
• A sequence of characters
• Stored in an array of type char
• Ending
• With the null character
• '\0'

7
Lecture Review

• A character string is a sequence of characters
  enclosed in double quotes ()
• E.g.
• char s12 a
• s10 a
• s11 \0
• char b abcdef
• char b10 abcdef
• char str
• It is called an empty string
• Uses one byte to store the null character (\0)
• char str101234567890 // invalid

8
Lecture Review

• cin stream operation
• char s10
• cin gtgt s
• A string with space ( ) CANNOT be read properly
• cin.getline
• Syntax
• cin.getline(char dst, int size, char delimiter)
• When the delimiter character is encountered
• A string is stored in character string dst
• With maximum length of size, including the null
  character (\0)
• Note
• delimiter character is optional, default is \n

9
Lecture Review

• What is the output of str in each case if the
  input is COMP102 is i-chi-ban?

char str30 cin.getline(str, 10)
COMP102 i
char str30 cin.getline(str, 10, 2)
COMP10
char str30 cin.getline(str, 16, -)
COMP102 is i
char str30 cin.getline(str, 25, i)
COMP102
char str30 cin.getline(str, 25)
COMP102 is i-chi-ban
10
Lecture Review

• String Copy
• NEVER use , except assign real val when
  declare
• char str16 Hello World
• char str116 str
• Copy source string into destination string
• void strcpy(char dest, const char src)
• E.g.
• strcpy(str1, str)

11
Lecture Review

• String Length
• int strlen(const char)
• Returns length of string, NOT include \0
• E.g.
• int str_length strlen(abcde)
• char str10 abcde
• int str_length strlen(str)

12
Lecture Review

• String Compare
• NEVER use (, lt, lt, gt, gt)
• Compares strings string1 and string2
• int strcmp(char string1, char string2)
• E.g.
• int result strcmp(s1, s2)
• if (s1 lt s2) gt result -1 (true)
• if (s1 s2) gt result 0 (false)
• if (s1 gt s2) gt result 1 (true)

13
Common Error

• The operator doesn't test two strings for
  equality
• E.g.
• if (string1 string2) // Invalid!
• Use strcmp function instead
• if (!strcmp(string1, string2))

14
SUMMARY

• By the end of this lab, you should be able to
• Pass array to function
• Declare and manipulate char array as string

15
Lab11

• Download the template from website