| new | statement |
| Syntax | A newStatement is:
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| Description | A new statement creates (allocates) a new element and assigns its location to the pointer variable. This element can be an object of a collection or class or a value of a type. If the collectionOrClassId is omitted, the choice of element is determined by the type of the pointer. For example, if the pointer is to class C, an object of class C will be allocated.
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| Example | Using a collection, declare a list of records and allocate one record.
var list : collection of
record
contents : string ( 10 )
next : pointer to list % Short form: next : ^ list
end record
var first : pointer to list % Short form: var first : ^ list
new list, first % Short form: new first
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| Example | Using a class, create an object of that class. The object is located by the start pointer.
class node
export var next, var name
name : string (25)
next : pointer to node % Short form: next : ^ node
end node
var start : pointer to node % Short form: var start : ^ node
new node, start % Short form: new start
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| Example | Using a record type, declare a list of records and allocate one record.
type item:
record
contents : string ( 10 )
next : pointer to item % Short form: next : ^ item
end record
var first : pointer to item % Short form: var first : ^ item
new first
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| Details | As the examples in this section show, a pointer can locate one of three things: an object of a collection, an object of a class or a value of a type. In the new statement, the collectionOrClassId can be omitted. If the pointer locates a type, it must be omitted. The free statement is used to deallocate an element. An imported class can have one of its objects created (by the new statement) only if the class is imported var. If there is no more space to allocate an element, new will set the pointer to be the nil value, and the program will continue executing. If the pointer locates class C and C contains an implement by list, the object created by new is the inherited object (through any number of levels of implement by). The pointer, however, remains a pointer to C. The form new p is a short form for new C, p when C is the class or collection given in p's type. If p is a pointer to class C and C has a descendant (expansion) class D, a new statement can be used to allocate an object of type D, as in:
new D, p % Allocates an object of class DIf D has an implement by clause, the expansion is created.
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| Details | The new statement can also be used to resize a flexible array. If an array has been declared flexible using the syntax .
var name : flexible array indexType { , indexType } of typeSpec
The indices may have compile-time or run-time upper bounds (the lower bound must be compile-time). The upper bounds can be changed by using:
new name , newUpper1 {,newUpper2}
The existing array entries will retain their values, except that any index made smaller will have the corresponding array entries lost. Any index made larger will have the new array entries uninitialized (if applicable).Additionally, the upper bound (both in the declaration and the new statement) can be made one less than the lower bound. This effectively makes an array that contains 0 elements. It can later be increased in size with another new. In the current implementation (1999), with a multi-dimensional array with a non-zero number of total elements, it is a run-time error to change any but the first dimension (unless one of the new upper bounds is one less than the corresponding lower bound, giving 0 elements in the array) as the algorithm to rearrange the element memory locations has not yet been implemented. Currently, only variables can be declared in this form. There is no flexible array parameter type, although a flexible array can be passed to an array parameter with "*" as the upper bound.
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| Example | See array for an example of flexible arrays.
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| See also | class and collection declarations, pointer type, free statement, nil value and implement by list. For flexible arrays, see also array and flexible.
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