l12_6up - MyString contd CSci 1113 C/C for Scientists and...

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CSci 1113
C/C++ for Scientists and Engineers
Section 010 - evening class
Pointers, Dynamic Arrays, Linked Lists
Prof. Eric Van Wyk and Ted Kaminski
Spring 2010
c Van Wyk and Kaminski
CSci 1113: C/C++ for Scientists and Engineers, evening class
Spring 2010 Page 1 / 27
MyString, cont’d :
Recap
Introduced pointer type.
char *str;
Comparison with fixed-size arrays.
Lets us have dynamically-sized arrays.
c Van Wyk and Kaminski
CSci 1113: C/C++ for Scientists and Engineers, evening class
Spring 2010 Page 2 / 27
MyString, cont’d :
Memory diagram
void f() {
int x;
int a[3];
int *b;
}
c Van Wyk and Kaminski
CSci 1113: C/C++ for Scientists and Engineers, evening class
Spring 2010 Page 3 / 27
MyString, cont’d :
Using dynamic arrays
int a[3];
int *b;
b = new int[3];
a[0] = 2;
b[0] = 2;
delete[] b;
c Van Wyk and Kaminski
CSci 1113: C/C++ for Scientists and Engineers, evening class
Spring 2010 Page 4 / 27
MyString, cont’d :
Stack memory management
C++ constructs all variables that come into scope
And destructs all variables going out of scope
Simple, predictable, safe.
c Van Wyk and Kaminski
CSci 1113: C/C++ for Scientists and Engineers, evening class
Spring 2010 Page 5 / 27
MyString, cont’d :
MyString
Implementation
c Van Wyk and Kaminski
CSci 1113: C/C++ for Scientists and Engineers, evening class
Spring 2010 Page 6 / 27

Pointer Basics :
We’ve seen some already.
Declaration.
Allocation/deletion of arrays.
Use of arrays.
Pointers are more than dynamic arrays.
c Van Wyk and Kaminski
CSci 1113: C/C++ for Scientists and Engineers, evening class
Spring 2010 Page 7 / 27
Pointer Basics :
&
“Address of” operator.
Obtain a pointer to something that already exists.
Unlike new where we create something.
c Van Wyk and Kaminski
CSci 1113: C/C++ for Scientists and Engineers, evening class
Spring 2010 Page 8 / 27
Pointer Basics :
*
“Dereference” operator.
Make use of what the pointer points to.
int *x = ...;
x is a pointer
*x is an integer
c Van Wyk and Kaminski
CSci 1113: C/C++ for Scientists and Engineers, evening class
Spring 2010 Page 9 / 27
Pointer Basics :
Pointer values
int *p = ...;
p = ...; changes where p points.
*p = ...; changes the memory where p points, which is
an integer.
c Van Wyk and Kaminski
CSci 1113: C/C++ for Scientists and Engineers, evening class
Spring 2010 Page 10 / 27
Pointer Basics :
new
& gives us the address of something existing.