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General Computer General Computer Science Science
for Engineersfor EngineersCISC 106CISC 106
Lecture 30Lecture 30
Dr. John CavazosComputer and Information Sciences
05/04/2009
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Lecture OverviewLecture OverviewDefinitions and PrototypesExamplesRead Chapter 5 (Ullman and
Singer)
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C++ Function DefinitionC++ Function DefinitionIs the code that implements a
function. Example 1: int main() { cout << “Hello World” << endl;}
Example 2: int squareArg(int x){ return x * 2;}
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C++ Function DefinitionC++ Function DefinitionExample 1: 1. int squareArg(int x)2. { 3. return x * 2;4. } 1.Return type, function name, argument
lists2.Open curly brace3.Function body
a) 0 or more return statements4.Close curly brace
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C++ Function DefinitionC++ Function DefinitionFunction can take multiple arguments
Example 1: int Power(int x, int n){ int powerof = x; for (int i =2; i<=n i++) powerof = powerof * x; return powerof;}
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C++ Function CallingC++ Function CallingMain function calls the function
squareArg.Example 1: int squareArg(int x){ return x * 2;}
int main() { int x = squareArg(100); cout << “square of 100 is ” << x <<
endl; }
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C++ Function PrototypesC++ Function PrototypesWhen you need to call a function
before you call itFunction prototypes have a specific
structure. They require the following parts:Return TypeFunction NameArgument (aka. Parameter) List
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C++ Function PrototypesC++ Function PrototypesHere is what a function prototype looks
like:
<return type> functionName(<parameter list>);
A simple function prototype as a demonstration:
int squareArg(int);
void printStudentName(string);
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C++ Function Prototype C++ Function Prototype ExampleExampleint i = 100;int squareArg(int); // function
prototypeint main() { d = squareArg(i);}
int squareArg(int x) // function definition
{ return x * 2;}
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C++ Function Calling C++ Function Calling Mistakes!Mistakes!int i = 100;int squareArg(int); // function
prototypeint main() { d = squareArg(“Hello”);}
int squareArg(int x) // function definition
{ return x * 2;}
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C++ Function Calling C++ Function Calling Mistakes!Mistakes!int i = 100;int squareArg(int); // function
prototypeint main() { d = squareArg(i);}
int squareArg(int x) // function definition
{ return “Hello”;}
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Putting all togetherPutting all togetherCreate a function to sum number
from 1 to NWhat do we need?
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C++ Functions: Putting all C++ Functions: Putting all togethertogether#include <iostream>using namespace std;
int sumFrom1ToN(int);int main() { int n = 0, sum = 0; cout << “Enter a number \n”; cin >> n; sum = sumFrom1ToN(n); cout << “The sum of numbers to ”
<< n; cout << “ is ” << sum << endl;} // the rest of program is on next slide
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C++ Functions: Putting all C++ Functions: Putting all togethertogether// main function above this
int sumFrom1ToN(int n) { int sum = 0; for (int i = 1; i <= n; i++) { sum = sum + i; } return sum;}