Kieren MacMillan <kieren_macmil...@sympatico.ca> writes:
> Hi David,
> Thank you for the helpful reply and documentation/explanation.
>> -- Function: ly:chain-assoc-get key achain default-value
>> Return value for KEY from a list of alists ACHAIN. If no entry is
>> found, return DEFAULT-VALUE or ‘#f’ if DEFAULT-VALUE is not
>> specified. [...]
>> DEFAULT-VALUE is specified as markp, and a markup is never #f. So your
>> condition is always true when the specified KEY cannot be found.
> So how could I code the when-property function so that it is false
> when the KEY cannot be found?
By not specifying a default value? I have absolutely no idea why you
put `markp' as the default-value of your call to ly:chain-assoc-get. It
does not serve any purpose conceivable to me, particularly since you are
only planning to use its value when finding the key, and the purpose of
the default-value is to be substituted when _not_ finding the key.
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