Programmer's Guide to the Zeno Interpreter

The Zeno language supports two categories of data, constants and variables. Constants and variables must be declared before they are used. This is done with a declaration statement. Variables provide you with a workspace for performing arithmetic and logical operations. Constants allow you to set values which cannot be changed during execution of your program; this can help you to reduce the likelihood of errors in your programs.

Variable declarations

Declarations of variables must have the following form:

    var name{, name} : type specification [:= expression]

Each name in the list is declared with the same type specification and is optionally initialized to the same expression value.

Constant declarations

Declaration of a constant uses this form:

    const name : type specification := constant expression

The syntax of a constant declaration is similar to that of a variable declaration; however, only one name at a time is declared. A constant must be initialized when it is declared. A constant expression is one that can be evaluated before the program is executed.

literal constants

A literal real number, that is, one written into your source code, begins and ends with a digit and must contain a decimal point. A unary operator, + or -, can optionally precede the first digit. The following forms are valid:

    -9.954                  % fixed point notation
     7.43e-4                % scientific notation