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C++: Difference between revisions
→Sequences
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* <code>dynamic_cast</code> | * <code>dynamic_cast</code> | ||
If you're casting between things but do not want to change the bit-pattern (e.g. binary data or pointers), you can also use <code>reinterpret_cast</code>. | If you're casting between things but do not want to change the bit-pattern (e.g. binary data or pointers), you can also use <code>reinterpret_cast</code>. | ||
===String=== | ===String=== | ||
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} | } | ||
</syntaxhighlight> | </syntaxhighlight> | ||
====Buildings Strings==== | |||
[https://www.fluentcpp.com/2017/12/19/build-strings-from-plain-string-up-to-boost-karma/ The Complete Guide to Building Strings In C++]<br> | |||
There are multiple ways of buildings strings in C++.<br> | |||
Strings are mutable in C++.<br> | |||
I typically use <code>+</code> or <code>ostringstream</code> to build strings. | |||
===Filesystem=== | ===Filesystem=== | ||
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===Sequences=== | ===Sequences=== | ||
====std::array==== | |||
<code>#include <array></code><br> | |||
In C++, you can use <code>std::vector</code> which gives you a resizable array. | |||
This will allocate an array in the heap.<br> | |||
[https://shendrick.net/Coding%20Tips/2015/03/15/cpparrayvsvector.html array vs vector]<br> | |||
If you need a static sized array, you can use <code>std::array</code> in the <code>array</code> header.<br> | |||
This wrapper around C-style arrays gives us size information and allows the array to be passed around by reference while keeping the array on the stack unlike <code>std::vector</code>.<br> | |||
If you want to allocate a static array on the heap, you can do so as follows: | |||
<syntaxhighlight lang="C++"> | |||
auto my_arr = std::make_shared<std::array<char,64>>(); | |||
</syntaxhighlight> | |||
====std::vector==== | ====std::vector==== | ||
[https://en.cppreference.com/w/cpp/container/vector Reference]<br> | |||
Use vector for almost everything...<br> | |||
It is an ArrayList.<br> | |||
Note that <code>vector<bool></code> is not an array of bools.<br> | |||
This has several nuances so you should use <code>vector<char></code> instead.<br> | |||
<syntaxhighlight lang="c++"> | |||
// Basics | |||
vector my_vec; | |||
// Vector with size 5 | |||
vector my_vec(5); | |||
// Vector with size 5 initialized to 1 | |||
vector my_vec(5, 1); | |||
// Length of vector | |||
my_vec.size(); | |||
// Equivalent to size()==0 | |||
my_vec.empty(); | |||
// Equivalent to my_vec[0]; | |||
// Undefined on empty vectors | |||
my_vec.front(); | |||
// Equivalent to my_vec[my_vec.size()-1]; | |||
// Undefined on empty vectors | |||
my_vec.back(); | |||
</syntaxhighlight> | |||
====std::deque==== | |||
Double-ended queue | |||
====std::list==== | ====std::list==== | ||
===Container adaptors=== | ===Container adaptors=== | ||
====std::queue==== | ====std::queue==== | ||
[https://en.cppreference.com/w/cpp/container/queue Reference]<br> | |||
<syntaxhighlight lang="c++"> | |||
</syntaxhighlight> | |||
====std::stack==== | ====std::stack==== | ||
[https://en.cppreference.com/w/cpp/container/stack cppreference] | [https://en.cppreference.com/w/cpp/container/stack cppreference] | ||
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</syntaxhighlight> | </syntaxhighlight> | ||
====std::unordered_map==== | ====std::unordered_map==== | ||
;Custom Keys | |||
How to use a rational number as a key in C++ | |||
<syntaxhighlight lang="C++"> | |||
struct Fraction | |||
{ | |||
int num; | |||
int den; | |||
bool operator==(const Fraction &other) const { | |||
return num*other.den == den * other.num; | |||
} | |||
Fraction(int a, int b) : num(a), den(b) {} | |||
}; | |||
</syntaxhighlight> | |||
==Boost== | ==Boost== | ||