The Script Programming Language

The Script Programming Language

Author: Jeff Stephenson
Date: 4 April 1988

Introduction

The Script adventure game language is an object-oriented language with a Lisp-like syntax. It is compiled by the sc compiler into the pseudo-code which is used by the interpreter, sci.

We will begin our discussion of the language with its basic Lisp-like characteristics, then go on to the object-oriented parts of the language.

As is Lisp, Script is based on parenthesized expressions which return values. An expression is of the form

Code:

(procedure [parameter parameter ...]).

The parameters to a procedure may themselves be expressions to be evaluated, and may be nested until you lose track of the parentheses.

Unlike Lisp, the procedure itself may NOT be the result of an evaluation. An example of an expression is

Code:

(+ (- y 2) (/ x 3))

which would be written in infix notation as

Code:

      (y - 2) + (x / 3).

All expressions are guaranteed to be evaluated from left to right. Thus,

Code:

(= x 4)
(= y (/ (+= x 4) (/= x 2)))

will result in y = 2 and x = 4.

Comments in Script begin with a semi-colon, ';', and continue to the end of the line.

Files

Source files for the script compiler have the extension .sc, header (include) files have the extension .sh. Source files may have any filename -- banner.sc and castle.sc are two examples. The output file from the compilation will have the name script.nnn where nnn is determined from the script# command (covered below) which is present in the file.

There are six files besides the source file and any user-defined header files which are involved in a compilation.

classdef

This file contains the information about the structure of the classes which have been defined in the application. It is read automatically by the compiler and is rewritten by the compiler after a successful compilation in order to keep it up to date. The user need not be concerned with it.