C++ Cheat Sheet: Quick Reference, Cheat Sheet of C programming

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C++ QUICK REFERENCE PREPROCESSOR // Comment to end of line /* Multi-line comment */ #include <stdio.h> // Insert standard header file #include "myfile.h" // Insert file in current directory #define X some text // Replace X with some text #define F(a,b) a+b // Replace F(1,2) with 1+2 #define X \ some text // Line continuation #undef X // Remove definition #if defined(X) // Condional compilation (#ifdef X) #else // Optional (#ifndef X or #if !defined(X)) #endif // Required after #if, #ifdef LITERALS 255, 0377, 0xff // Integers (decimal, octal, hex) 2147483647L, 0x7fffffffl // Long (32-bit) integers 123.0, 1.23e2 // double (real) numbers 'a', '\141', '\x61' // Character (literal, octal, hex) '\n', '\\', '\'', '\"' // Newline, backslash, single quote, double quote "string\n" // Array of characters ending with newline and \0 "hello" "world" // Concatenated strings true, false // bool constants 1 and 0 DECLARATIONS int x; // Declare x to be an integer (value undefined) int x=255; // Declare and initialize x to 255 short s; long l; // Usually 16 or 32 bit integer (int may be either) char c='a'; // Usually 8 bit character unsigned char u=255; signed char s=-1; // char might be either unsigned long x=0xffffffffL; // short, int, long are signed float f; double d; // Single or double precision real (never unsigned) bool b=true; // true or false, may also use int (1 or 0) int a, b, c; // Multiple declarations int a[10]; // Array of 10 ints (a[0] through a[9]) int a[]={0,1,2}; // Initialized array (or a[3]={0,1,2}; ) int a[2][3]={{1,2,3},{4,5,6}}; // Array of array of ints char s[]="hello"; // String (6 elements including '\0') int* p; // p is a pointer to (address of) int char* s="hello"; // s points to unnamed array containing "hello" void* p=NULL; // Address of untyped memory (NULL is 0) int& r=x; // r is a reference to (alias of) int x enum weekend {SAT,SUN}; // weekend is a type with values SAT and SUN enum weekend day; // day is a variable of type weekend enum weekend {SAT=0,SUN=1}; // Explicit representation as int enum {SAT,SUN} day; // Anonymous enum typedef String char*; // String s; means char* s; const int c=3; // Constants must be initialized, cannot assign to const int* p=a; // Contents of p (elements of a) are constant int* const p=a; // p (but not contents) are constant const int* const p=a; // Both p and its contents are constant const int& cr=x; // cr cannot be assigned to change x STORAGE CLASSES int x; // Auto (memory exists only while in scope) static int x; // Global lifetime even if local scope extern int x; // Information only, declared elsewhere STATEMENTS x=y; // Every expression is a statement int x; // Declarations are statements ; // Empty statement { // A block is a single statement int x; // Scope of x is from declaration to end of block a; // In C, declarations must precede statements } if (x) a; // If x is true (not 0), evaluate a else if (y) b; // If not x and y (optional, may be repeated) else c; // If not x and not y (optional) while (x) a; // Repeat 0 or more times while x is true for (x; y; z) a; // Equivalent to: x; while(y) {a; z;} do a; while (x); // Equivalent to: a; while(x) a; switch (x) { // x must be int case X1: a; // If x == X1 (must be a const), jump here case X2: b; // Else if x == X2, jump here default: c; // Else jump here (optional) } break; // Jump out of while, do, or for loop, or switch continue; // Jump to bottom of while, do, or for loop return x; // Return x from function to caller try { a; } catch (T t) { b; } // If a throws a T, then jump here catch (...) { c; } // If a throws something else, jump here FUNCTIONS int f(int x, int); // f is a function taking 2 ints and returning int void f(); // f is a procedure taking no arguments void f(int a=0); // f() is equivalent to f(0) f(); // Default return type is int inline f(); // Optimize for speed f() { statements; } // Function definition (must be global) T operator+(T x, T y); // a+b (if type T) calls operator+(a, b) T operator-(T x); // -a calls function operator-(a) T operator++(int); // postfix ++ or -- (parameter ignored) extern "C" {void f();} // f() was compiled in C Function parameters and return values may be of any type. A function must either be declared or defined before it is used. It may be declared first and defined later. Every program consists of a set of a set of global variable declarations and a set of function definitions (possibly in separate files), one of which must be: int main() { statements... } or int main(int argc, char* argv[]) { statements... } argv is an array of argc strings from the command line. By convention, main returns status 0 if successful, 1 or higher for errors. Functions with different parameters may have the same name (overloading). Operators except :: . .* ?: may be overloaded. Precedence order is not affected. New operators may not be created. EXPRESSIONS Operators are grouped by precedence, highest first. Unary operators and assignment evaluate right to left. All others are left to right. Precedence does not affect order of evaluation, which is undefined. There are no run time checks for arrays out of bounds, invalid pointers, etc. T::X // Name X defined in class T N::X // Name X defined in namespace N ::X // Global name X t.x // Member x of struct or class t p->x // Member x of struct or class pointed to by p a[i] // i'th element of array a f(x,y) // Call to function f with arguments x and y T(x,y) // Object of class T initialized with x and y x++ // Add 1 to x, evaluates to original x (postfix) x-- // Subtract 1 from x, evaluates to original x typeid(x) // Type of x typeid(T) // Equals typeid(x) if x is a T dynamic_cast<T>(x) // Converts x to a T, checked at run time static_cast<T>(x) // Converts x to a T, not checked reinterpret_cast<T>(x) // Interpret bits of x as a T const_cast<T>(x) // Converts x to same type T but not const sizeof x // Number of bytes used to represent object x sizeof(T) // Number of bytes to represent type T ++x // Add 1 to x, evaluates to new value (prefix) --x // Subtract 1 from x, evaluates to new value ~x // Bitwise complement of x !x // true if x is 0, else false (1 or 0 in C) -x // Unary minus +x // Unary plus (default) &x // Address of x *p // Contents of address p (*&x equals x) new T // Address of newly allocated T object new T(x, y) // Address of a T initialized with x, y new T[x] // Address of allocated n-element array of T delete p // Destroy and free object at address p delete[] p // Destroy and free array of objects at p (T) x // Convert x to T (obsolete, use .._cast<T>(x)) x * y // Multiply x / y // Divide (integers round toward 0) x % y // Modulo (result has sign of x) x + y // Add, or &x[y] x - y // Subtract, or number of elements from *x to *y x << y // x shifted y bits to left (x * pow(2, y)) x >> y // x shifted y bits to right (x / pow(2, y)) x < y // Less than x <= y // Less than or equal to x > y // Greater than x >= y // Greater than or equal to x == y // Equals x != y // Not equals x & y // Bitwise and (3 & 6 is 2) x ^ y // Bitwise exclusive or (3 ^ 6 is 5) x | y // Bitwise or (3 | 6 is 7) x && y // x and then y (evaluates y only if x (not 0)) x || y // x or else y (evaluates y only if x is false (0)) x = y // Assign y to x, returns new value of x x += y // x = x + y, also -= *= /= <<= >>= &= |= ^= x ? y : z // y if x is true (nonzero), else z throw x // Throw exception, aborts if not caught x , y // evaluates x and y, returns y (seldom used) CLASSES class T { // A new type private: // Section accessible only to T's member functions protected: // Also accessable to classes derived from T public: // Accessable to all int x; // Member data void f(); // Member function void g() {return;} // Inline member function void h() const; // Does not modify any data members int operator+(int y); // t+y means t.operator+(y) int operator-(); // -t means t.operator-() T(): x(1) {} // Constructor with initialization list T(const T& t): x(t.x) {} // Copy constructor T& operator=(const T& t) {x=t.x; return *this; } // Assignment operator ~T(); // Destructor (automatic cleanup routine) explicit T(int a); // Allow t=T(3) but not t=3 operator int() const {return x;} // Allows int(t) friend void i(); // Global function i() has private access friend class U; // Members of class U have private access static int y; // Data shared by all T objects static void l(); // Shared code. May access y but not x class Z {}; // Nested class T::Z typedef int V; // T::V means int }; void T::f() { // Code for member function f of class T this->x = x;} // this is address of self (means x=x;) int T::y = 2; // Initialization of static member (required) T::l(); // Call to static member