string name = "John Xhu";
cout << name << endl;
size_t space_index = name.find(' '); // size_t: type for value return by collections
cout << "Index of space: " << space_index << endl;
if ( space_index == string::npos )
cout << "Not found" << endl;
cout << "Initials: " << name[0] << name[space_index + 1] << endl;
todo.cpp
string operator[](int ix) { .... }
We will discuss this later!!
+---------------+
|Type |
| |
|field: ___ |
|field: ___ | +----------------+
|field: O------+------------->|Type |
| | | |
+---------------+ |field: ____ |
+----------------+
class A {
public:
int f();
private:
int num;
};
// untested, from http://tinyurl.com/zy8scsu
#include <math.h>
double sqrt(double x) {
if (x <= 0)
return 0; // if negative number throw an exception?
int exp = 0;
x = frexp(x, &exp); // extract binary exponent from x
if (exp & 1) { // we want exponent to be even
exp--;
x *= 2;
}
double y = (1+x)/2; // first approximation
double z = 0;
while (y != z) { // yes, we CAN compare doubles here!
z = y;
y = (y + x / y) / 2;
}
return ldexp(y, exp / 2); // multiply answer by 2^(exp/2)
}
class ToDo {
public:
ToDo();
ToDo(string first_item);
bool empty();
bool full();
void add(string next_item);
string next_item();
// returns the next item capitalized; this is to illustrate converting
// a string to upper case; use tolower to convert to lower case.
string next_item_capitalized();
private:
static constexpr int MAXITEMS = 100;
string items[MAXITEMS];
int count;
};
ToDo::ToDo() : count{0} { }
ToDo::ToDo(string first_item) : count{1} {
items[0] = first_item;
}
bool ToDo::empty() {
return count <= 0;
}
bool ToDo::full() {
return count >= MAXITEMS;
}
void ToDo::add(string next_item) {
if ( full() )
throw "Adding item to full todo list.";
items[count] = next_item;
++count;
}
string ToDo::next_item() {
if ( empty() )
throw "Removing item from empty todo list.";
string result = items[0];
for(int i = 0; i < count - 1; ++i)
items[i] = items[i + 1];
--count;
return result;
}
string ToDo::next_item_capitalized() {
string item = next_item();
// note use of size_t to initialize i; this avoids warnings when
// comparing i to item.length() (since item.length() is generally unsigned)
for(size_t i = 0; i < item.length(); ++i)
item[i] = toupper(item[i]);
return item;
}
void set_up_today() {
ToDo stuff_to_do;
stuff_to_do.add("sleep");
stuff_to_do.add("study");
stuff_to_do.remove("sleep");
...
ToDo *todays_activities = new ToDo();
todays_activities->add("eat");
->
instead of .
*distance = 4.5;
g++ -S pointers.cpp
is in the file pointers.s
float *nums = new float[100];
allocates 100 floats on the heap and stores it in nums
float *temp = new float[200];
for(int i = 0; i < 100; ++i)
temp[i] = nums[i];
nums = temp;
ToDo class:
class ToDo {
public:
ToDo();
bool empty();
bool full();
void add(string next_item);
string next_item();
private:
string *items;
int count, capacity;
};
ToDo::ToDo() : count{0}, capacity{100}, items{new string[100]} { }
bool ToDo::empty() { return count == 0; }
bool ToDo::full() { return false; } // WHY?
void ToDo::add(string next_item) {
if ( count >= capacity ) {
string *old_items = items;
items = new string[capacity * 2];
capacity *= 2;
for(int i = 0; i < count; ++i)
items[i] = old_items[i];
delete[] old_items;
}
items[count] = next_item;
++count;
}
string ToDo::next_item() {
if ( empty() )
throw "Removing item from empty todo list.";
string result = items[0];
for(int i = 0; i < count - 1; ++i)
items[i] = items[i + 1];
--count;
return result;
}