Complements?

Clueless in Ohio asks:
Are these infinitives functioning as complements?
Jim doesn't know when to quit drinking.
Jim doesn't know how to fix the printer.
Jim doesn't know where to register tomorrow.
Jim didn't know whether to laugh or cry.

And if all those are complements, what grammar role does when, how, where, and whether play?

According to my dictionary, a complement describes or identifies the subject or the direct object:
He is the treasurer. (subjective complement)
She is talented. (subjective complement)

We elected him treasurer. (objective complement)
The prize made her happy. (objective complement)

The sentences you supplied don't have complements—they have adverbs or conjunctions that link infinitive phrases to the verb "know." Each linked phrase tells us what Jim doesn't know: when to quit drinking, how to fix the printer, and so on. In the last sentence, "whether" is a conjunction linking "to laugh" and "to cry," and again the function is to modify "know."

Comments

[kevin]

Hi,
I have a question regarding subjective complement?
In the sentence below, what are the subject and subjective complement.
Thank you

Sentence: The name of my town is Herndon.

[michael murphy]

In the sentence, "Jim didn't know whether to laugh or to cry," "whether...or" are correlative conjunctions. They link the double direct object, "to laugh" and "to cry."

In the sentence, "The name of my town is Herndon," the simple subject is "name," and the subjective/predicate complement is "Herndon."

Incidentally, the COMPLETE subject is "The name of my town."