Parse$

Definition from the manual:

Read-only engine variable that contains either the offending portion of an invalid input line or any section of the input line enclosed in quotes.

In any given input line, parse$ can be several different things. If every word in the input line is an understood dictionary entry, parse$ is set to “”. If the input line has no quoted text but some words (or numbers) are not in the dictionary table, parse$ is set to the last not-understood word.

The numerical value of parse$ can change as well. Regular command parsing set it as -1 (as described in the Hugo Book), but if the command was the result of the input being called, parse$ is given the value of 0.

It’s also important to remember that since parse$ is during the engine’s parsing phase, at the time of the game loop where Parse and PreParse are called, parse$ has not been set yet. See “Replace Parse” and “Replace ParseError”.

Pages with parse$

Some uses of parse$: Comments In Transcripts uses parse$ to determine if the first character of the input line is an asterisk. StringToNumber (routine) uses parse$ for entering numbers. StringDictCompare uses it to write quoted text to a string. dict (routine) will show how to use parse$ to name objects in-game (like the Beyond Zork naming mechanic).

parse$ in parser messages

parse$ gets set to interesting things in error messages. Their specific behavior is good to know, especially when writing new error messages.

ParseError Number	When Called	parse$ value
1	Not-understood word in input	First misunderstood word
3	Tried to use ALL with a verb that doesn’t support it	Set to the verb word
5	Player’s command didn’t match any object but all words are in the dictionary	Object, as it was referred to
9	No objects available to	Set to the verb word
10	Object isn’t known.	Object, as it was referred to
11	Known object not in current location	Object, as it was referred to
12	Can’t do something (like, talking to a non-living object)	Object, as it was referred to