More doc updates

[substrate.git] / documentation / zil.md

diff --git a/documentation/zil.md b/documentation/zil.md
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--- a/documentation/zil.md
+++ b/documentation/zil.md
@@ -1,6 +1,9 @@
-# Zork Implentation Language
-This document covers the Zork Implementation Language, as originally 
-developed and used by Infocom for their games.
+# Introduction
+This document covers the Zork Implementation Language, or ZIL for 
+short, as originally developed and used by Infocom for their games.
+
+ZIL is a subset of the MIT Design Language, or MDL for short, and 
+pronounced as "Muddle". MDL is itself based on classic LISP.

 
 ## Format
 This document is written using CommonMark, a markup language. More 
 
 ## Format
 This document is written using CommonMark, a markup language. More 


@@ -17,17 +20,63 @@ License along with this document. If not see
 <https://gnu.org/licenses/>.
 
 ## Definitions
 <https://gnu.org/licenses/>.
 
 ## Definitions

-

 A "definition" is used to describe a room, object, routine, etc. in or 
 used by the game. Each definition consists of a number of properties, 
 flags, and/or instructions. A program written in ZIL can be thought of 
 A "definition" is used to describe a room, object, routine, etc. in or 
 used by the game. Each definition consists of a number of properties, 
 flags, and/or instructions. A program written in ZIL can be thought of 

-as consisting of one or more of these definitions. Definitions, 
-properties, flags, and instructions include brackets which must be 
-correctly paired and nested.
+as consisting of two or more of these definitions. At a minimum, a 
+program must define which version it is to be compiled for and contain 
+at least one routine named GO from which execution begins. 
+Definitions, properties, flags, and instructions include brackets 
+which must be correctly paired and nested.
+
+## Z-machine versions
+Infocom made 6 versions of the Z-machine. The community made 2 more, 
+for a total of 8, mostly to support larger story files. To define 
+which version of the Z-machine a program is to be compiled for, it 
+must contain a VERSION definition at the top level, outside any other 
+definitions, in the following format, using this BNF-style syntax:
+
+    <version-definition> ::= "<" "VERSION" <version-number> ">"
+
+    <version-number> ::= "ZIP" | "EZIP" | "XZIP" | "YZIP" | "1" | "2"
+    | "3" | "4" | "5" | "6" | "7" | "8"
+
+ZIP is equivalent to version 3, EZIP to version 4, XZIP to version 5, 
+and YZIP to version 6.
+
+## Comments
+Comments are ignored by the compiler. A comment begins with a 
+semicolon (;) and continues until the end of the line. A multiline 
+comment also begins with a semicolon but is enclosed in double quotes. 
+However, single line comments may also be enclosed in double quotes. 
+While comments may be placed anywhere in a source code file, a comment 
+may not be placed inside an atom.
+
+## Parser
+The purpose of the parser is to receive and process the player's 
+input. Its primary responsibility is to determine the player's 
+intended action along with any objects that may be referred to.
+
+The player's action is referred to internally as the PRSA (think "A" 
+for action like "EAT", the direct object as PRSO (think "O" for 
+"object") and the indirect object as PRSI (think "I" for indirect.)
+
+For an example, the command "KILL TROLL WITH SWORD" would set the PRSA 
+to KILL and the PRSO to TROLL and PRSI to SWORD. It is important to 
+note that not all instructions from the player will necessarily have 
+all three things, but a PRSA is required in all cases and you can't 
+have a PRSI without also having a PRSO. In cases where there is no 
+PRSI or PRSO, they are set to false.
+
+Note that the PRSA isn't simply the word that the player entered. The 
+PRSA from a given sentence is determined by the syntax definitions in 
+the game. An example being: The player might type "CONSUME APPLE" but 
+in the game's syntax definitions, the PRSA associated with "consume" 
+might be EAT.

 
 ## Syntax Definitions
 Syntax definitions are used by the parser to determine valid sentence 
 
 ## Syntax Definitions
 Syntax definitions are used by the parser to determine valid sentence 

-structures.
+structures. Each entry must correspond to this format:

 
 A simple example might be:
 
 
 A simple example might be:
 


@@ -36,3 +85,5 @@ A simple example might be:
 Using this example, should the parser match the player's input to 
 "xyzzy" then the PRSA is set to magic. PRSI and PRSO would be set to 
 false.
 Using this example, should the parser match the player's input to 
 "xyzzy" then the PRSA is set to magic. PRSI and PRSO would be set to 
 false.

+
+## Syntax Tokens