Read/Write Variables

A read/write variable (RWV) is a named storage that holds a data. The data can be any EDEN data structure. There is no need to declare a variable before it is used. Memory storage is allocated when the variable name first appears in a program. Data can be assigned to RWV's using assignment statements. For example,

V = 1;

The identifier (name) V denotes an RWV whose value is assigned to integer 1 by the operator =. The semi-colon terminates the statement.

The value of an RWV is referenced if its name appears in an expression. If the RWV has not been assigned a value before its value is referenced, the value @ (meaning ``undefined'') is assigned to it automatically.

Different typed data can be assigned to the same variable at different time. The EDEN interpreter checks for data type clash at run-time.

The interpreter assumes all objects are RWV's until they are defined to be functions, formula definitions or action specifications.