Dynamic Arrays动态数组.pptVIP

Classes Dynamic Arrays by Briana Morrison adapted from Dale/Weems/Headington and Cahoon/Davidson Topics Dynamic Arrays Class Specification Class Implementation Destructors Deep Copies Copy Constructor Assignment Operator This Pointer Inline Functions Constructor Initialization Lists Dynamically Sized Lists Up until now all lists (arrays) have had a fixed size, determined at compile time int a[10]; // holds maximum of 10 int and there is possible wasted space Using dynamic memory allocation, we can size the list during execution of the program IntPtr a = new int[10]; Operator new Syntax new DataType new DataType [IntExpression] If memory is available, in an area called the heap (or free store) new allocates the requested object or array, and returns a pointer to (address of ) the memory allocated. Otherwise, program terminates with error message. The dynamically allocated object exists until the delete operator destroys it. Dynamic Array Allocation Operator delete Syntax delete Pointer delete [ ] Pointer If the value of the pointer is 0 there is no effect. Otherwise, the object or array currently pointed to by Pointer is deallocated, and the value of Pointer is undefined. The memory is returned to the free store. Square brackets are used with delete to deallocate a dynamically allocated array. A Simple Dynamic List Type What we want An integer list data type DynArray that allows run-time specification of size. Also prevents indexes from going out of bounds and aggregate array copying and initialization Features and abilities True object Can be passed by value and reference Can be assigned and copied Inspect and mutate individual elements Inspect list size Print and read a list Sample DynArray Usage DynArray beta(5); //create array of 5 elements beta.Store (75, 2); // store value 75 at location 2 DynArray gamma(4,1); // create array of 4 elements gamma.Store (-8, 2); // store value -8 at location 2 cout gamma.ValueAt(2);