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CSCE 110 PROGRAMMING FUNDAMENTALS
WITH C++
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WITH C++ Prof. Amr Goneid AUC Part 6. Simple and User Defined - - PowerPoint PPT Presentation
WITH C++ Prof. Amr Goneid AUC Part 6. Simple and User Defined - - PowerPoint PPT Presentation
CSCE 110 PROGRAMMING FUNDAMENTALS WITH C++ Prof. Amr Goneid AUC Part 6. Simple and User Defined Data Types Prof. amr Goneid, AUC 1 More on Simple Data Types Prof. amr Goneid, AUC 2 More on Simple Data Types #define Directive
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More on Simple Data Types
#define Directive Promotion of Types Type Casting typedef Declaration Enumerated Data Types
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- 1. #define Directive
Used to give meaningful names to constants Used in older C programs prior to introduction of
constants #define <token> <replacement-text>
Example
#define pi 3.14159 // The same as const float pi = 3.14159;
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#define Directive (Example)
// File: try.cpp // Uses #define Directive #include <iostream> using namespace std; #define BEGIN { #define END } #define MOD % #define EQ ==
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#define Directive (Example)
int main() BEGIN // Local data ... int n , d ; cout << "Enter n : "; cin >> n ; for ( ; ; ) BEGIN d = n MOD 2; cout << d; n /= 2; if (n EQ 0) break; END cout << endl; return 0; END
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- 2. Promotion of Types
Type promotion
promoting a lower type to a higher type, e.g.
3 + x /2
if x is float, constants would be promoted to float
as well and actually be 2.0 and 3.0
Type conversions
int to float (number.0) float to int (truncation occurs)
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Mixing Types
Example: float x , z ; int y; x = 3.89 ; y = x ; z = y ; // y would contain 3 and z would contain 3.0
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Avoid mixing types but if you need to you can cast a
type
Type casting allows you to change a type within the
program for a specific function
Form:
type (variable)
- r (type) variable
Example:
int n ; float sum , average ; average = sum / float (n); // or average = sum / (float) n ;
- 3. Type Casting
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Type Casting Example
Example:
for (j = 0; j <= 25; j++) { for (k = 0; k <= j; k++) cout << char (int (‘A’) + k); cout << endl; }
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Used to give other names to existing data
- types. The new name can then be used as
a qualified data type. Original type remains active.
Syntax:
typedef <C++ type> <other name> ;
- 4. typedef Declaration
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typedef Declaration
Examples:
typedef int itemtype ; typedef float costType ; typedef char gradeType ; ……… itemtype item ; …… item = 7 ; costtype cost ; …… cost = 21.36 ; gradetype grade ; …grade = ‘B’ ;
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- 5. Enumerated Data Types
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Of course C++ will give errors for the
following declarations:
icecream scoop ; fruit summerfruit ; color thiscolor ; …………… scoop = vanilla; summerfruit = mango; thiscolor = red ; fruit2 = fruit (int(mango) + 1);
How can we make C++ accept these types?
Enumerated Data Types
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Enumerated Types
Enumerated Data Types:
Create new ordinal data types by enumerating their elements in ascending rank ( 0 , 1 ,2 …).
Example:
enum weekday {Sun , Mon , Tue , Wed , Thu , Fri , Sat}; ……. weekday day ; day = Mon ;
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Using Enumerated Types
All operations on ordinal types can be
performed on enumerated types. enum classid {freshman, sophomore, junior, senior}; classid newClass; if (newClass == freshman) do something else if (newClass == sophomore) …..
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Examples: enum color {red,green,blue,yellow}; color color1,color2, c ; color1 = red; color2 = color (int(green) +1); for(c = red; c <= yellow; c++) cout << int(c) << “ “ ; cout << endl; color1 = color (3); if(color1 > blue) cout << “yellow”; 0 1 2 3 yellow
Using Enumerated Types
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Example: color.cpp
// DISPLAYS THE VALUE OF thisColor void writeColor (color thisColor) { switch (thisColor) { case red: cout << "red"; break; case green: cout << "green"; break;
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color.cpp
case blue: cout << "blue"; break; case yellow: cout << "yellow"; break; default: status = 0; cerr << "*** ERROR: Invalid color value." << endl; } }
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Explicit Enumeration
C++ allows to give explicit values to
- enumerators. For Example:
enum NumberBase { Binary = 2, Octal = 8, Decimal = 10, Hexa = 16};
We can also start from a number other than
- zero. For example: