Chapter 9. CLAUSE: Find the Noun Clause Boundaries

• Arguments: Start address of clause, Preposition number of clause, Vocabulary address of current token
• Return: Address to start of clause, -1 if no tokens are left to process, or FALSE if error in clause syntax

9.1 Introduction

CLAUSE will find the end address of a noun clause and saves the start and end addresses for this clause along with the preposition information in ITBL. P-NCN (noun clause number) indicates if the direct (1) or indirect (2) object clause is being processed. Specific locations in ITBL for the extracted information to be stored are calculated depending on P-NCN.

	Direct Object (Noun 1) Clause	Indirect Object (Noun 2) Clause
Preposition Number	Word 2	Word 4
Vocabulary Address of Preposition	Word 3	Word 5
Address of First Token (Start)	Word 6	Word 8
Address after Last Token (End)	Word 7	Word 9

9.2 How it screens...

CLAUSE loops through tokens in LEXV as long as the given tokens are part of a valid syntax for a noun clause. Briefly, the routine will

1. Save any preposition information (number and address) if it exists into the proper locations in ITBL.

1. The preposition information is usually passed as an argument. CLAUSE will then find the Vocabulary address of the preposition.
2. If no preposition is given or exists, $00 is saved as the preposition number and address

2. Save the start address of the noun clause into the proper location in ITBL.
3. Attempt to get the next token to process as well.
4. Loop through the tokens in LEXV as long as the given tokens are part of a valid syntax for a noun clause (see rules below)

Once the routine stopped checking for tokens, it can return three possible results: FALSE if there was a syntax error, -1 if no more tokens left to process, or offset to the last token in the newly found clause. The address after the end of the newly found clause will be saved in the proper location in ITBL for the end address of the clause.

Type	Example	Action
Unmatched		Display error & return
Conjunction (“and” or “,”)	Eat apple and orange	Set ANDFLAG & continue
Quantity (“all” or “one”)	Take all bananas	Continue
Quantity (“all” or “one”) + “of”	Burn one of the letters	Skip “of” token & continue
End-of-command “then” or “.”	Throw hammer then go west	Save end address of current noun clause and return
Preposition (not the first token in the clause)	Put letter inside mailbox	Save end address of current noun clause and return
Noun (also an Adjective) + Noun	Drop gold coin	Continue
Noun and ANDFLAG set	Eat apple and orange and grape	Clear ANDFLAG & continue
Noun and ANDFLAG clear and next token is an exception (“but” or “exception”) or conjunction token	Eat apple and orange Eat all fruit except banana	Continue
Noun	Turn statue	Save end address of current noun clause & return
Adjective	Read brown book	Continue
Special (not Conjunction, Quantity, or End-of-command)	Push the button	Continue
All others (verbs or direction) and ANDFLAG set	Ignite red match and go east	Change conjunction token to “then” and go back 2 tokens to process again*
All others (verbs or direction) and ANDFLAG clear	Cut rope go north	Display “Can’t Use” error & return

*For example:

        get candle and eat apple

                     ^

is converted to:

        get candle then eat apple

                 ^                

with CLAUSE going back to the conjunction token to reprocess the clause. The routine will recognize “then” as an end-of-command token, marking the end of a clause.

9.3 Update: New Matches…

Later Infocom games added more acceptable token combination for clauses which caused CLAUSE to also grow. Outside of specialized tokens used in specific games (such as spell names in Spellbreaker), the new and improved CLAUSE mainly became more sophisticated on deciding what part of speech a token was being based upon its context with other tokens. The major additional rules created by Infocom are below:

Type	Example	Action	Game
Articles ("the","a","an")	Eat an apple	Skip over token & continue	Deadline
Unmatched and NUMBER? is true	Take 2 candles	Unmatched token changed to “intnum”, global var set to value, & continue	Deadline
“of” and verb = “accuse”	Accuse Bob of murder	Change “of” to “with” & continue	Deadline
“.” and previous token is a title (“mrs”,”mr”,”ms”, “dr”, “st”)	Ask Mr. Smith about paper	Continue	Deadline, LGOP
Preposition (first token checked)	Throw out ball	Continue	Zork 1-R88
Preposition (prep value already given in argument)		Skip over token & continue	LGOP
Preposition (can also be an adjective) and a prep has already been give	Write on back side	Assume preposition is an adjective and continue	Bureaucracy
Noun (can also be adjective) and next token is noun or adj or direction	Drop gold coin Take copper hot rod	Assume noun is an adjective & Continue	HGTG, Moonmist
Adjective AND P-MERGED/ P-OFLAG set or verb given	Green Get Green	Continue	Zork 1-R88
Special (not Conjunction, Quantity, or End-of-command) AND P-MERGED/ P-OFLAG set or verb given	A red Get a red	Continue	Zork 1-R88
All others (verb, direction) and ANDFLAG set and verb given	Ignite red match and go east	Change conjunction token to “then” and go back 2 tokens & continue	Seastalker
Profanity, interrogatives	Eat banana who	Display error message & stop	LGOP, Trinity