Modula-3: New

# New

An allocation operation has the form:

        NEW(T, ...)

where `T` is a reference type other than `REFANY`, `ADDRESS`, or `NULL`. The operation returns the address of a newly-allocated variable of `T`'s referent type; or if `T` is an object type, a newly-allocated data record paired with a method suite. The reference returned by `NEW` is distinct from all existing references. The allocated type of the new reference is `T`.

It is a static error if `T`'s referent type is empty. If `T` is declared as an opaque type, `NEW(T)` is legal only in scopes where `T`'s concrete type is known completely, or is known to be an object type.

The initial state of the referent generally represents an arbitrary value of its type. If `T` is an object type or a reference to a record or open array then `NEW` takes additional arguments to control the initial state of the new variable.

If `T` is a reference to an array with k open dimensions, the `NEW` operation has the form:

        NEW(T, n_1, ..., n_k)

where the `n`'s are integer-valued expressions that specify the lengths of the new array in its first k dimensions. The values in the array will be arbitrary values of their type.

If `T` is an object type or a reference to a record, the `NEW` operation has the form:

        NEW(T, Bindings)

where `Bindings` is a list of keyword bindings used to initialize the new fields. Positional bindings are not allowed.

Each binding `f := v` initializes the field `f` to the value `v`. Fields for which no binding is supplied will be initialized to their defaults if they have defaults; otherwise they will be initialized to arbitrary values of their types.

The order of the field bindings makes no difference.

If `T` is an object type then `Bindings` can also include method overrides of the form `m := P`, where `m` is a method of `T` and `P` is a top-level procedure constant. This is syntactic sugar for the allocation of a subtype of `T` that includes the given overrides, in the given order. For example, `NEW(T, m := P)` is sugar for

        NEW(T OBJECT OVERRIDES m := P END).

    Last modified on Wed Apr  3 09:39:02 PST 1996 by heydon
         modified on Mon Apr 18 14:04:40 PDT 1994 by kalsow