Lecture02.pdf

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CS and the Honor Code
Alternate final exam
•
I relented. Will offer final Th Mar 20 12:15-3:15pm. Absolutely NO
other alternates.
C++ vs Java: what’s the same?
General syntax
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comment sequence
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use of braces, parentheses, commas, semi-colons
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variable/parameter declarations, function call
Primitive variable types
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char, int, double, but note Java boolean is C++ bool
Cafe hangout today after class in Terman — join us!
Today’s topics
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C++ syntax and structure, procedural paradigm
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User-defined types, parameter passing
Operators
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arithmetic, relational, logical
Control structures
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for, while, if/else, switch, return
Reading
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Handout 4, Reader Ch. 1, 2.1, 2.6 (today)
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Ch. 3(next)
Lecture #2
Dissecting a C++ program
/*
* average.cpp
* ------------
* This program adds scores and prints their average.
*/
#include "genlib.h"
#include "simpio.h"
#include <iostream>
const int NumScores = 4;
double GetScoresAndAverage(int numScores);
int main()
{
cout << "This program averages " << NumScores << " scores." << endl;
double average = GetScoresAndAverage(NumScores);
cout << "The average is " << average << "." << endl;
return 0;
}
average.cpp (cont’d)
/* Function: GetScoresAndAverage
* Usage: avg = GetScoresAndAverage(10);
* -------------------------------------
* This function prompts the user for a set of values and returns
* the average.
*/
double GetScoresAndAverage(int numScores)
{
int sum = 0;
for (int i = 0; i < numScores; i++) {
cout << "Next score? ";
int nextScore = GetInteger();
sum += nextScore;
}
return double(sum)/numScores;
}
C++ user-defined types
Enumerations
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Define new type with set of constrained options
enum directionT {North, South, East, West};
directionT dir = East;
if (dir == West) ...
C++ parameter passing
Default is
pass-by-value
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Parameter copies value, changes affect local copy
void Binky(int x, int y)
{
x *= 2;
y = 0;
}
int main()
{
int a = 4, b = 20;
Binky(a, b);
...
Records
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Define new type which aggregates a set of fields
struct pointT {
double x;
double y;
};
pointT p, q;
p.x = 0;
p = q;
Add & to declaration for
pass-by-reference
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Parameter is now reference to original variable, which can change
void Binky(int &x, int y)
{
x *= 2;
y = 0;
}
int main()
{
int a = 4, b = 20;
Binky(a, b);
...
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Ref param also used for efficiency to avoid copying large data
C++ libraries
Groups related operations
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Header file provides function prototypes and usage comments
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Compiled library contains implementation
C++ standard libraries
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e.g. string, iostream, fstream
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#include <iostream>
getline substr
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Terse, lowercase names:
cout
CS106 libraries
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e.g. simpio, random, graphics
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#include “random.h”
RandomChange
DrawLine
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Capitalized verbose names:
GetInteger

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