
                             STRUCTS

struct sname { f1,...,fn; };   struct declaration
new sname(e1, ..., en)         struct instantiation
s . fi ;                       struct component selection
s . fi = e ;                   struct component update

Structs are data structures whose components may be selected by name.
The typical operations are declaration, instantiation, selection and
update.

A struct declaration is essentially a class declaration which defines
the names of the components of the struct. The syntax of the declaration
is best shown by an example.

struct item {partno, code, quantity;};

The above declaration defines item to be a struct with the (field)
names partno, code and quantity. Various items can be instantiated
(created) by providing the struct name and values for the fields.
(but a struct component may not be a function).

i1=new item(124,"receipt",15);
i2=new item(126,"issue",7);

Components of structs may be selected using a dot notation similar
to records in Pascal and structures in C.

i1.code;                   returns "receipt"
i2.quantity;               returns 7

Component values may be updated using assignment and dot notation.

i1.quantity=22;            assigns 22 as the new value of the quantity
                           field.
