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Morten Nobel-Joergensen
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README.md
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README.md
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# C++ QUICK REFERENCE / C++ CHEATSHEET
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Based on <a href="http://www.pa.msu.edu/~duxbury/courses/phy480/Cpp_refcard.pdf">Phillip M. Duxbury's C++ Cheatsheet</a> and edited by Morten Nobel-Jørgensen.
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The cheatsheet focus on C++ - not on the library.
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C++11 additions is inspired by <a href="https://isocpp.org/blog/2012/12/c11-a-cheat-sheet-alex-sinyakov">ISOCPP.org C++11 Cheatsheet</a>).
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The goal is to give a concise overview of basic, modern C++.
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The document is hosted on XXX. Any comments and feedback are appreciated.
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## PREPROCESSOR
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~~~~
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// Comment to end of line
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/* Multi-line comment */
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#include <stdio.h> // Insert standard header file
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include "myfile.h" // Insert file in current directory
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#define X some text // Replace X with some text
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#define F(a,b) a+b // Replace F(1,2) with 1+2
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#define X \
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some text // Multiline definition
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#undef X // Remove definition
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#if defined(X) // Condional compilation (#ifdef X)
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#else // Optional (#ifndef X or #if !defined(X))
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#endif // Required after #if, #ifdef
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~~~~
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## LITERALS
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~~~~
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255, 0377, 0xff // Integers (decimal, octal, hex)
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2147483647L, 0x7fffffffl // Long (32-bit) integers
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123.0, 1.23e2 // double (real) numbers
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'a', '\141', '\x61' // Character (literal, octal, hex)
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'\n', '\\', '\'', '\"' // Newline, backslash, single quote, double quote
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"string\n" // Array of characters ending with newline and \0
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"hello" "world" // Concatenated strings
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true, false // bool constants 1 and 0
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nullptr // Pointer type with the address of 0
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~~~~
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## DECLARATIONS
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~~~~
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int x; // Declare x to be an integer (value undefined)
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int x=255; // Declare and initialize x to 255
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short s; long l; // Usually 16 or 32 bit integer (int may be either)
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char c='a'; // Usually 8 bit character
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unsigned char u=255;
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signed char s=-1; // char might be either
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unsigned long x =
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0xffffffffL; // short, int, long are signed
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float f; double d; // Single or double precision real (never unsigned)
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bool b=true; // true or false, may also use int (1 or 0)
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int a, b, c; // Multiple declarations
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int a[10]; // Array of 10 ints (a[0] through a[9])
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int a[]={0,1,2}; // Initialized array (or a[3]={0,1,2}; )
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int a[2][2]={{1,2},{4,5}}; // Array of array of ints
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char s[]="hello"; // String (6 elements including '\0')
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std::string s = "Hello" // Creates string object with value "Hello"
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std::string s = R"(Hello
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World)"; // Creates string object with value "Hello\nWorld"
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int* p; // p is a pointer to (address of) int
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char* s="hello"; // s points to unnamed array containing "hello"
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void* p=nullptr; // Address of untyped memory (nullptr is 0)
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int& r=x; // r is a reference to (alias of) int x
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enum weekend {SAT,SUN}; // weekend is a type with values SAT and SUN
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enum weekend day; // day is a variable of type weekend
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enum weekend{SAT=0,SUN=1}; // Explicit representation as int
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enum {SAT,SUN} day; // Anonymous enum
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enum class Color {Red,Blue};// Color is a strict type with values Red and Blue
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Color x = Color::Red; // Assign Color x to red
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typedef String char*; // String s; means char* s;
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const int c=3; // Constants must be initialized, cannot assign to
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const int* p=a; // Contents of p (elements of a) are constant
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int* const p=a; // p (but not contents) are constant
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const int* const p=a; // Both p and its contents are constant
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const int& cr=x; // cr cannot be assigned to change x
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int8_t,uint8_t,int16_t,
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uint16_t,int32_t,uint32_t,
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int64_t,uint64_t // Fixed length standard types
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auto it = m.begin(); // Declares it to the result of m.begin()
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auto const param = config["param"];
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// Declares it to the const result
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auto& s = singleton::instance();
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// Declares it to a reference of the result
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~~~~
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## STORAGE CLASSES
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~~~~
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int x; // Auto (memory exists only while in scope)
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static int x; // Global lifetime even if local scope
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extern int x; // Information only, declared elsewhere
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~~~~
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## STATEMENTS
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~~~~
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x=y; // Every expression is a statement
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int x; // Declarations are statements
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; // Empty statement
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{ // A block is a single statement
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int x; // Scope of x is from declaration to end of block
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}
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if (x) a; // If x is true (not 0), evaluate a
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else if (y) b; // If not x and y (optional, may be repeated)
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else c; // If not x and not y (optional)
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while (x) a; // Repeat 0 or more times while x is true
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for (x; y; z) a; // Equivalent to: x; while(y) {a; z;}
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for (x : y) a; // Range-based for loop e.g.
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// for (auto& x in someList) x.y();
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do a; while (x); // Equivalent to: a; while(x) a;
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switch (x) { // x must be int
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case X1: a; // If x == X1 (must be a const), jump here
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case X2: b; // Else if x == X2, jump here
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default: c; // Else jump here (optional)
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}
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break; // Jump out of while, do, or for loop, or switch
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continue; // Jump to bottom of while, do, or for loop
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return x; // Return x from function to caller
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try { a; }
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catch (T t) { b; } // If a throws a T, then jump here
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catch (...) { c; } // If a throws something else, jump here
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~~~~
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## FUNCTIONS
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~~~~
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int f(int x, int); // f is a function taking 2 ints and returning int
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void f(); // f is a procedure taking no arguments
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void f(int a=0); // f() is equivalent to f(0)
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f(); // Default return type is int
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inline f(); // Optimize for speed
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f() { statements; } // Function definition (must be global)
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T operator+(T x, T y); // a+b (if type T) calls operator+(a, b)
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T operator-(T x); // -a calls function operator-(a)
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T operator++(int); // postfix ++ or -- (parameter ignored)
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extern "C" {void f();} // f() was compiled in C
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~~~~
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Function parameters and return values may be of any type. A function must either be declared or defined before
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it is used. It may be declared first and defined later. Every program consists of a set of a set of global variable
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declarations and a set of function definitions (possibly in separate files), one of which must be:
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~~~~
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int main() { statements... } or
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int main(int argc, char* argv[]) { statements... }
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~~~~
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argv is an array of argc strings from the command line. By convention, main returns status 0 if successful, 1 or
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higher for errors.
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Functions with different parameters may have the same name (overloading). Operators except :: . .* ?: may be
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overloaded. Precedence order is not affected. New operators may not be created.
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## EXPRESSIONS
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Operators are grouped by precedence, highest first. Unary operators and assignment evaluate right to left. All
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others are left to right. Precedence does not affect order of evaluation, which is undefined. There are no run time
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checks for arrays out of bounds, invalid pointers, etc.
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~~~~
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T::X // Name X defined in class T
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N::X // Name X defined in namespace N
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::X // Global name X
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t.x // Member x of struct or class t
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p-> x // Member x of struct or class pointed to by p
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a[i] // i'th element of array a
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f(x,y) // Call to function f with arguments x and y
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T(x,y) // Object of class T initialized with x and y
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x++ // Add 1 to x, evaluates to original x (postfix)
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x-- // Subtract 1 from x, evaluates to original x
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typeid(x) // Type of x
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typeid(T) // Equals typeid(x) if x is a T
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dynamic_cast< T>(x) // Converts x to a T, checked at run time
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static_cast< T>(x) // Converts x to a T, not checked
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reinterpret_cast< T>(x) // Interpret bits of x as a T
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const_cast< T>(x) // Converts x to same type T but not const
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sizeof x // Number of bytes used to represent object x
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sizeof(T) // Number of bytes to represent type T
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++x // Add 1 to x, evaluates to new value (prefix)
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--x // Subtract 1 from x, evaluates to new value
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~x // Bitwise complement of x
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!x // true if x is 0, else false (1 or 0 in C)
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-x // Unary minus
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+x // Unary plus (default)
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&x // Address of x
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*p // Contents of address p (*&x equals x)
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new T // Address of newly allocated T object
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new T(x, y) // Address of a T initialized with x, y
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new T[x] // Address of allocated n-element array of T
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delete p // Destroy and free object at address p
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delete[] p // Destroy and free array of objects at p
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(T) x // Convert x to T (obsolete, use .._cast<T>(x))
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x * y // Multiply
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x / y // Divide (integers round toward 0)
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x \% y // Modulo (result has sign of x)
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\\
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x + y // Add, or \&x[y]
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x - y // Subtract, or number of elements from *x to *y
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x << y // x shifted y bits to left (x * pow(2, y))
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x >> y // x shifted y bits to right (x / pow(2, y))
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x < y // Less than
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x <= y // Less than or equal to
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x > y // Greater than
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x >= y // Greater than or equal to
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x & y // Bitwise and (3 & 6 is 2)
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x ^ y // Bitwise exclusive or (3 ^ 6 is 5)
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x | y // Bitwise or (3 | 6 is 7)
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x && y // x and then y (evaluates y only if x (not 0))
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x || y // x or else y (evaluates y only if x is false (0))
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x = y // Assign y to x, returns new value of x
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x += y // x = x + y, also -= *= /= <<= >>= &= |= ^=
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x ? y : z // y if x is true (nonzero), else z
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throw x // Throw exception, aborts if not caught
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x , y // evaluates x and y, returns y (seldom used)
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~~~~
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## CLASSES
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~~~~
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class T { // A new type
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private: // Section accessible only to T's member functions
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protected: // Also accessable to classes derived from T
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public: // Accessable to all
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int x; // Member data
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void f(); // Member function
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void g() {return;} // Inline member function
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void h() const; // Does not modify any data members
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int operator+(int y); // t+y means t.operator+(y)
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int operator-(); // -t means t.operator-()
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T(): x(1) {} // Constructor with initialization list
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T(const T& t): x(t.x) {}// Copy constructor
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T& operator=(const T& t)
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{x=t.x; return *this; } // Assignment operator
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~T(); // Destructor (automatic cleanup routine)
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explicit T(int a); // Allow t=T(3) but not t=3
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T(float x): T((int)x) {}// Delegate contructor to T(int)
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operator int() const
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{return x;} // Allows int(t)
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friend void i(); // Global function i() has private access
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friend class U; // Members of class U have private access
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static int y; // Data shared by all T objects
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static void l(); // Shared code. May access y but not x
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class Z {}; // Nested class T::Z
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typedef int V; // T::V means int
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};
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void T::f() { // Code for member function f of class T
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this->x = x;} // this is address of self (means x=x;)
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int T::y = 2; // Initialization of static member (required)
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T::l(); // Call to static member
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T t; // Create object t implicit call constructor
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t.f(); // Call method f on object t
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struct T { // Equivalent to: class T { public:
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virtual void i(); // May be overridden at run time by derived class
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virtual void g()=0; }; // Must be overridden (pure virtual)
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class U: public T { // Derived class U inherits all members of base T
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public:
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void g(int) override; }; // Override method g
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class V: private T {}; // Inherited members of T become private
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class W: public T, public U {};
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// Multiple inheritance
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class X: public virtual T {};
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// Classes derived from X have base T directly
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~~~~
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All classes have a default copy constructor, assignment operator, and destructor, which perform the
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corresponding operations on each data member and each base class as shown above. There is also a default no-argument
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constructor (required to create arrays) if the class has no constructors. Constructors, assignment, and
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destructors do not inherit.
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## TEMPLATES
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~~~~
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template <class T> T f(T t);// Overload f for all types
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template <class T> class X {// Class with type parameter T
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X(T t); }; // A constructor
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template <class T> X<T>::X(T t) {}
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// Definition of constructor
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X<int> x(3); // An object of type "X of int"
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template <class T, class U=T, int n=0>
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// Template with default parameters
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~~~~
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## NAMESPACES
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~~~~
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namespace N {class T {};} // Hide name T
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N::T t; // Use name T in namespace N
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using namespace N; // Make T visible without N::
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~~~~
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