Computer Science Introduction to C++pages.cpsc.ucalgary.ca/~hhornbec/moodle/cpp_intro/cpp_intro.pdf · Housekeeping Introductory Courses Quick introductions Refresh knowledge Tease

Introduction to C++

Haysn Hornbeck

Computer Science

Housekeeping

Online Survey

What do you use?

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https://goo.gl/forms/pyipArU6IG4gUgxu1

Housekeeping

Introductory Courses

● Quick introductions● Refresh knowledge● Tease full courses?

3


Housekeeping

● Intro to Linux● Advanced Linux● Intro to C++● Code Repositories● Pointers and Indirection● Designing OO Programs● Debugging in Eclipse● Memory management

4https://moodle.cpsc.ucalgary.ca/


Housekeeping

Materials (CompSci)

● UofC IT account(see HelpDesk)

● Remote Loginhttp://www.ucalgary.ca/cpsc/tech/services/remote_access_samba

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Housekeeping

Materials(not CompSci)

● Mac OS XLibraries, Various odd places

● Bootable USB keyshttps://rufus.akeo.ie/http://unetbootin.github.io/

● Virtual Machineshttps://virtualboxes.org/images/

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https://rufus.akeo.ie/

http://unetbootin.github.io/

Housekeeping

Online Survey

7


HistoryC

8

History

1966

BCPL

9https://www.bell-labs.com/usr/dmr/www/bcpl.pdf

BCPL

GET "LIBHDR"

// calculate factorials

LET START() = VALOF $(

FOR I = 1 TO 5 DO

WRITEF("%N! = %I4*N", I, FACT(I))

RESULTIS 0

$)

AND FACT(N) = N = 0 -> 1, N * FACT(N - 1)

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https://en.wikipedia.org/wiki/BCPL#Examples

BCPL

• First to use code blocks• Two-step compilation• Procedures with parameters and return• Only one data type, 16-bit word• Pointers

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History

1969

B

12

B

13https://www.bell-labs.com/usr/dmr/www/kbman.html

main() { extrn fact, printn, putchar; auto i, r;

i = 1; while(i<6) { printn( fact(i), 10 ); putchar( ‘*n’ ); /* ‘*n’ = newline */

i =+ 1; }}

printn(n,b) {extrn putchar;auto a;

if(a=n/b) /* assign and check */printn(a, b);

putchar(n%b + '0'); /* exploit ASCII encoding */}

fact(n) { if(n<2) return 1; else return n * fact(n-1);}

History

1972

Unix on the PDP-11

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History

1972

C

15

C

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#include <stdio.h>

int fact( n ) {

if (n<2)return 1;

elsereturn n * fact(n-1);

}

int main( int argc, char* argv[] ) {

int i = 1;

while (i<6)printf( “%f\n”, fact(i++) );

return 0;}

C

• Multiple fundamental data types• Structures• Static types, weak enforcement• Weak array support• Multi-step compilation

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Multiple Data Types

bool

char

short

int

long

long long

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unsigned char

unsigned short

unsigned int

unsigned long

unsigned long long

float

double

Structures

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// by tagname

struct point {

float x;float y;

};

struct point p;

// by alias

typedef struct {

float x;float y;

} point;

point p;// tagname → aliastypedef struct point d2;

d2 p;

Static Types, Weak Enforcement

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// all these are valid

long first = 17592186044416;int second = 16777216;char third = first + second;

int fourth = 4.0134;

float pi = 3.14159274;int fifth = *(int*)π

Static Types, Weak Enforcement

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// all these are valid

long first = 17592186044416;int second = 16777216;char third = first + second; // 0

int fourth = 4.0134; // 4

float pi = 3.14159274;int fifth = *(int*)π // 1078530011 ?!

Weak Array Support

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int array[5];

for (int it = 0; it < 11; it++)array[it] = it; // this works?!

Weak Array Support

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int array[5];

for (int it = 0; it < 11; it++)array[it] = it; // this works?!

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 150 char** argv int argc

16 Array[0] Array[1] Array[2] Array[3]32 Array[4 ] float pi48 int fifth int fourth char third int second64 long first

Multi-step Compilation

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Preprocessor(insert files, expand macros)

Compile(convert to assembly code)

Assemble(convert to machine code)

Link(combine parts and libraries)

Preprocessor

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main.cpp

shared.h stdio.h

main.cpp

shared.h

stdio.h

Compile

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main.cpp

shared.h

stdio.h

main.asm

Assembly Language

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.file "test.c" .text .globl main .type main, @functionmain:.LFB0: .cfi_startproc pushq %rbp .cfi_def_cfa_offset 16 .cfi_offset 6, -16 movq %rsp, %rbp .cfi_def_cfa_register 6 movl %edi, -68(%rbp) movq %rsi, -80(%rbp) movabsq $17592186044416, %rax movq %rax, -16(%rbp) movl $16777216, -20(%rbp) movl -20(%rbp), %eax movl %eax, %edx movq -16(%rbp), %rax addl %edx, %eax movb %al, -21(%rbp) movl $4, -28(%rbp) movss .LC0(%rip), %xmm0 movss %xmm0, -36(%rbp) leaq -36(%rbp), %rax movl (%rax), %eax movl %eax, -32(%rbp) movl $0, -4(%rbp) jmp .L2.L3: movl -4(%rbp), %eax cltq movl -4(%rbp), %edx movl %edx, -64(%rbp,%rax,4) addl $1, -4(%rbp)

.L2: cmpl $10, -4(%rbp) jle .L3 movl $0, %eax popq %rbp .cfi_def_cfa 7, 8 ret .cfi_endproc.LFE0: .size main, .-main .section .rodata .align 4.LC0: .long 1078530011 .ident "GCC: (Debian 6.2.1-5) 6.2.1 20161124" .section .note.GNU-stack,"",@progbits

main.asm

Assemble

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main.bin

Link

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main.bin

stdio.bin

processing.bin

main.bin

stdio.bin

processing.bin

Why C Stinks

● Poor organization● Side effects galore● “Trust the coder”

● Pointers

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History

1967

Simula 67

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Simula 67

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Class Rectangle (Width, Height); Real Width, Height; ! Class with two parameters; Begin Real Area, Perimeter; ! Attributes; Procedure Update; ! Methods (Can be Virtual); Begin Area := Width * Height; Perimeter := 2*(Width + Height) End of Update; Boolean Procedure IsSquare; IsSquare := Width=Height; Update; ! Life of rectangle started at creation; OutText("Rectangle created: "); OutFix(Width,2,6); OutFix(Height,2,6); OutImage End of Rectangle;

History

1979

C with Classes

33

History

1983

C++

34

History

1989

C++ 2.0

35

History

1998

ISO/IEC 14882:1998(C++98)

36

History

37

1998 2003

2011 2014

2017

Demo Code

38

Demo Code

39

√(x−xo)2+( y−yo)

2= r

π =circumference

diameter

Demo Code

40

|x−xo|+|y− yo| = r

π =circumference

diameter

Demo Code

41

|x−xo|+|y− yo| = r

π = 4

Demo Code

42

3√(x−xo)3+( y− yo)

3 = r

π ≈ 3.259767993

Demo Code

43

p√(x−xo)p+( y− yo)

p = r

π = ?

https://en.wikipedia.org/wiki/Lp_space#The_p-norm_in_finite_dimensions

Classes, Attributes, Methods, ...

44

class PiEstimator {

private: CircleGenerator cg; // used to create points set<Point> points; // the points that make up our arc

public: PiEstimator( fp p );

fp getP() { return cg.getP(); } void setP( fp p );

// estimate Pi via a lot of "random" points fp estimateViaFlood( ulong count );

// estimate Pi via distance segmentation fp estimateViaSegment( fp maxDist );

}; // PiEstimator

Typedef

45

typedef unsigned long ulong;

typedef double fp;

Inheritence, Virtual Functions

46

class DistanceMetric {

public: static virtual fp distance( const& Point, const& Point );

}; // DistanceMetric

class EuclideanDistance : public DistanceMetric {

public: static fp distance( const& Point a, const& Point b ) {

return sqrt( (a.getX() - b.getX())*(a.getX() - b.getX()) + (a.getY() - b.getY())*(a.getY() - b.getY()) ); }};

Operator Overloading

47

class Point {

private: fp x; // the coordinates of this point in 2D space fp y;

public: /* .... */

// so we're organized in set bool operator<( const Point& a ) const;

// to make some operations easier Point operator+( const Point& a ) const; Point operator-( const Point& a ) const; Point operator*( const fp& a ); Point power( const fp& a ); Point absolute();

}; // Point


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class Point {


public: /* .... */



}; // PointPoint a;Point b;

Point c = a – b; // Point c( a.getX() - b.getX(), a.getY() - b.getY() );

Inheritence, Virtual Functions

49

class DistanceMetric {

public: static virtual fp distance( const& Point, const& Point );

}; // DistanceMetric

class EuclideanDistance : public DistanceMetric {

public: static fp distance( const& Point a, const& Point b ) {

// return sqrt( (a.getX() - b.getX())*(a.getX() - b.getX()) +// (a.getY() - b.getY())*(a.getY() - b.getY()) );

return ((a – b).dot(a – b)).sqrt(); }};

Input / Output

50

#include <stdio.h>

printf( “For precision %f and exponent %f, Pi ~= %.15f\n”, precision, exponent, pe.estimateViaSegment( precision ) );

using std::cout;using std::endl;using std::setprecision;#include <iostream>

std::cout << "For precision " << precision << " and exponent " << exponent << ", Pi ~= " << std::setprecision(15) << pe.estimateViaSegment( precision ) << std::endl;

Namespaces

51

#include <stdio.h>


#include <iostream>using std::cout;using std::endl;using std::setprecision;

cout << "For precision " << precision << " and exponent " << exponent << ", Pi ~= " << setprecision(15) << pe.estimateViaSegment( precision ) << endl;

Namespaces

52

#include <stdio.h>


#include <iostream>using std::cout;using std::endl;using std::setprecision;

cout << "For precision " << precision << " and exponent " << exponent << ", Pi ~= " << setprecision(15) << pe.estimateViaSegment( precision ) << endl;

// Point Point::operator+( const Point& a ) const;

Namespaces

53

// creating a namespacenamespace myPackage {

class myClass {

public:void doSomething();

};

}

// “importing” from a namespace

using myPackage::myClass;

myClass.doSomething();

Namespaces

54

Point Point::pow( const fp& s ) { // doesn’t compile

return Point( pow(x,s), pow(y,s) );}

Point Point::power( const fp& s ) {

return Point( pow(x,s), pow(y,s) );}

Templates

55

class PairPoints {

private:

Point a;Point b;

public:

Point first() { return a; }Point second() { return b; }

};

Templates

56

template <class T>;class Pair {

private:

T a;T b;

public:

T first() { return a; }T second() { return b; }

};

Pair<Point> ray;

Template Specialization

57

template <class T>;class Pair {

// assume it’s a pass-by-valuebool lessThan( const& T rhs ) { return *this < rhs; }

// ...

template <>;class Pair<T*> {

// know we have a referencebool lessThan( const& T rhs ) { return **this < *rhs; }

// ...

Standard Template Library

58

Vector

List

Set

Map

Queue

Array

- Dynamic array

- Linked list

- Ordered list

- Key -> value

- First in, First out

- Fixed-size array


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class Point {


public: /* .... */



}; // Point

Memory Management

60

// CPoint* point = (Point*) malloc( sizeof(Point) );Point* array = (Point*) malloc( sizeof(Point) * count );

free(point);free(array);

// C++Point* point = new Point();Point* array = new Point[3];std::vector<Point> better;

delete point;delete[] array; // quite important!

But...

C++ = Cwith some added syntactic sugar

61

C++ = C

● All C operators work

● “main” function still around

● Ditto pointers

● Preprocessor and garbage dependency handling

● Compile-time enforcement

● Permissive casting

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C++ = C

30+ years of development● More libraries than any other language

● Interfaces to other languages

● Ported everywhere

● The Boost libraries

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64

LabChallenges

http://pages.cpsc.ucalgary.ca/~hhornbec/moodle/cpp_intro/

65

G++

(GNU C compiler)

http://pages.cpsc.ucalgary.ca/~hhornbec/moodle/cpp_intro/

-o [file] -g

-ggdb-O[number]-I [directory]

-l [file]

The file to output to.Add debugging symbols.Add debugging symbols for GDB.Optimize the code, to varying levels. [0-3]Search for header files in this directory, too.Link in this library, too.

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Computer Science Introduction to C++pages.cpsc.ucalgary.ca/~hhornbec/moodle/cpp_intro/cpp_intro.pdf · Housekeeping Introductory Courses Quick introductions Refresh knowledge Tease