Routines
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AFB7: Parser: Validate Any Direct Object
Used by the routines at Action_Jump, Action_Climb, Action_Go and Action_Swim.
In most adventure games, the structure for a command is "verb + direct object". This is usually how the player interacts with the game world. The verb describes the action, and the direct object is what the action is performed on. For example; "TAKE SHOE" uses the verb "TAKE" on the direct object "SHOE".
Output
A The number of valid direct objects in the user input tokens
F The carry flag is set when the command is malformed
F The zero flag is set when there are no valid direct objects present in the input tokens
The first token is the verb, so target the second token for the direct object.
Parser_ValidateAnyDirectObject AFB7 LD A,($A825) Fetch the second token from the user input and store it in A.
AFBA CP $FF Jump forward to ValidateAnyDirectObject if the token is anything other than the terminator character (FF).
AFBC JR NZ,ValidateAnyDirectObject
The token was the terminator character (FF), so the sentence is malformed.
E.g. They tried "TAKE" but didn't write anything after it.
Print "Please be more specific.".
AFBE CALL Response_PleaseBeMoreSpecific Call Response_PleaseBeMoreSpecific.
AFC1 SCF Set the carry flag to indicate this call was a failure.
AFC2 RET Return.
The user input tokens have a direct object, return how many are in the command buffer.
ValidateAnyDirectObject AFC3 CALL Parser_CountItems Call Parser_CountItems.
AFC6 RET Return.
View the equivalent code in The Jewels Of Babylon.
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