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From C to C++
From C to C++
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Why C++ is much more fun than C (C++ FAQ)?
1. Classes & methods - OO design
2. Generic programming - Templates allow
for code reuse
3. Stricter type system (e.g. function args)
4. Some run-time checks & memory control
A common and mature language that
gives you high level and low level control Have fun
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Why C++ is much more fun than c (C+ FQA)?
1. Tons of corner cases
2. Duplicate features
3. Cryptic syntax
4. Undecidable syntax (uncompilable progarms!)
5. No two compilers agree on it
Probably one of the hardest computer
languages to master. Have fun
History
4
The C++ Prog. Manual (85-
90) C++98 C++03 C++11 C++14
Default in
g++
Minor
changes
auto,
lambdas,
threading,
…
Auto
return
type,
generic
lambdas,
binary
literals,…
Minor
changes
Major
changes
History
5
The C++ Prog. Manual (85-
90) C++98 C++03 C++11 C++14
Default in
g++
Minor
changes
auto,
lambdas,
threading,
…
Auto
return
type,
generic
lambdas,
binary
literals,…
Minor
changes
Major
changes
We’ll learn parts of C++-11, Mostly parts that makes C++ more “pythonic”
while keeping it efficient
Course Objectives
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1. Learn the language
2. Practice of programming data structures
Design
Testing & Debugging
Efficiency & Portability
Modularity
Course structure
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• The basic mechanism underlying many of the extensions.
Overloading
• The C++ version. Object Oriented
programing
• A hidden monster Copying and Conversion
• Templates - Generics++. Compile time
polymorphism
• Statics, etc. Other topics
First Program in C++
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// This line includes the standard // I/O
library file (similar to “copy here this
file”)
#include <iostream>
int main()
{
std::cout << "Hello class!\n";
return 0;
}
Compiling & Running…
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In this course we’ll use ubuntu standalone or c9io (ubuntu on the cloud) with the gcc (gnu compiler collection):
> g++ -Wall -Wvla -Werror -g -D_GLIBCXX_DEBUG -std=c++11 –Wall hello.cpp –o hello
> hello
Hello class!
>
Fill in missing types from C, in somewhat
crude way
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The missing types
strings in C++
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#include <iostream> #include <string> int main() { std::string str; int a; double b; std::cin >> str >> a >> b; if(std::cin.fail()) { std::cerr << "input problem\n"; return 1; } std::cout << "I got: "<< str << ' ' << a << ' ' << b << std::endl; }
More about string functions:
http://www.cppreference.com/cppstring
Boolean variables
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#include <iostream>
int main()
{
int a = 5;
bool isZero = (a == 0);
// same conditions
if(!isZero && isZero==false &&
isZero!=true && !!! isZero && a )
{
std::cout << "a is not zero\n";
}
}
Enum (C)
User Defined Type - enum
Enumerated data - a set of named constants.
Usage: enum [identifier]{enumerator list}
enum Season {
WINTER, // = 0 by default
SPRING, // = WINTER + 1
SUMMER, // = WINTER + 2
AUTUMN // = WINTER + 3
};
enum {SUNDAY=1, MONDAY, TUESDAY, …}; // nameless
enum Color {BLACK,RED,GREEN,YELLOW,BLUE,WHITE=7,GRAY};
// 0 1 2 3 4 7 8
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enum
enum Season curr_season;
curr_season= AUTUMN;
curr_season= 19; // legal, but ugly, g++: warning
int SUMMER; // error, redefinition
int prev_season = SUMMER; // legal, but ugly, g++ warning
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enum Season {
WINTER, // = 0 by default
SPRING, // = WINTER + 1
SUMMER, // = WINTER + 2
AUTUMN // = WINTER + 3
};
Use enum to eliminate magic
numbers – alternative to #define
#include <stdio.h>
#include <stdlib.h>
enum{INPUT_FILE_NAME = 1,OUTPUT_FILE_NAME,ARGS_NUM};
int main(int argc, char* argv[])
{
if(argc != ARGS_NUM)
{
printf("usage: wc <input file name> <output file name>\n");
exit(1);
}
FILE* inFile, outFile;
inFile = fopen(argv[INPUT_FILE_NAME],"r");
if( inFile == NULL)
{
printf("error reading file: %s\n", argv[INPUT_FILE_NAME]);
exit(1);
}
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C++-11 enum class
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Season curr_season;
curr_season= Season::AUTUMN;
curr_season= SUMMER; // won’t compile!
curr_season= 19; // won’t compile!
int prev_season= Season::SUMMER; // won’t compile!
enum class Season : char {
WINTER, // = 0 by default
SPRING, // = WINTER + 1
SUMMER, // = WINTER + 2
AUTUMN // = WINTER + 3
};
enums – why?
More readable code
Code less error prone
Accessible for debugger
Use of the numerical values is not disabled
bad programming usually!
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Understand and remember.
• More than syntactic sugar.
• This is how a lot of stuff works under
the hood (e.g. inheritance)
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Overloading
#include <stdio.h> void foo() { printf ("foo()\n"); } void foo(int n) { printf ("foo(%d)\n", n); } int main() { foo(12); foo(); return 0; }
Function overloading - C
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Compilation output:
Error: Multiple definition of foo
Function overloading – C++
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#include <iostream> void foo() { std::cout << "foo()\n"; } void foo(int n) { std::cout<<"foo("<<n<<")\n"; } int main() { foo(12); foo(); }
Output:
Compile, and print: foo(12) foo()
Default parameters
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#include <iostream> void foo(int n=5) { std::cout << n; } int main() { foo(); }
Output:
Compile, and print: foo(5)
Overload resolution
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1. Find all functions with same name “candidates”. Let’s
call them Ω1
2. Find Ω2 ⊆ Ω1 which have the correct number of
arguments - “viable candidates”
3. Find Ω3 ⊆ Ω2 with best matching arguments.
if Ω3 = 1:
use that function.
else (0 or more than 1):
emit compilation error.
