Present participle with an infinitive

The common usage is that "looking forward to" expects a noun or a gerund
to follow. "To" is not part of an infinitive in this case.

You are looking forward to present what, exactly?

The clause is incomplete.

Thanks. I can see that, but isn't "looking" and "hoping" the same part of speech? As such, why is it OK to say "hoping" + infinitive but not "looking" + infinitive, if they're the same parts of speech (present participle). I'm hoping (no pun intended) to understand the reason, e.g., you can't mix a present participle with an infinitive (although, clearly, you can). Is there an actual rule/reason why one is right but the other isn't? Or is it purely idiomatic?

Thanks for the reply, but couldn't you use that argument with, "I'm hoping to present tomorrow", where it's understood that you will be giving a presentation (on what is academic)?
Consider the following:
"How did your presentation go?"
"It didn't happen, but I'm hoping to present tomorrow instead"

The "to" after "looking forward" is a preposition whose object is the gerund
"presenting".

The "to" after "hoping" is part of the infinitive "to present".

Hmm, according to the American Heritage Dictionary, "present" can be used intransitively.

Yes; that makes sense, but I don't understand how that relates my conundrum? Why can you use an infinitive after a present participle in one sentence but not the other?

So, are you stumped too?

Let's make this clearer by removing the "present participle" factor.

Change
"I am looking forward to present tomorrow"
and
"I am hoping to present tomorrow"
to
"I look forward to present tomorrow"
and
"I hope to present tomorrow".

Notice that the first is still incorrect and the second is still correct even
without "present participles".

That's because in this case "to present" IS NOT AN INFINITIVE.

In this sentence "look forward" is modified by a prepositional phrase
indicating that to which one is looking forward. The phrase is incorrect
because "present" is not a noun and cannot be the object of a preposition.
(Of course, if tomorrow is your birthday, you can look forward
to "presents".)

I --> subject
look (or "am looking") --> verb
forward --> adverb
to --> preposition
present --> object of the preposition
tomorrow --> adverb

Thanks for your reply, and sorry for the delay in coming back to you.
I agree, then, that's it's not an issue with mixing a present participle with an infinitive; therefore, by taking your initiative and by bringing it back to its most basic form . . .
I <subject> hope <verb> to present tomorrow
I <subject> look <verb> to present tomorrow

Is it because look is a transitive verb but hope is a linking verb?

Interesting that you've dropped "forward" from the second sentence.

Now you are using "look" in a different sense, one that is used with the
infinitive. If you check the definition of "look" at the Merriam-Webster site,
you will find

4 a : expect, anticipate <we look to have a good year>
b : to have in mind as an end <looking to win back some lost profits>

So now both sentences are correct.

So, it's forward that causes the problem? If so, why is that exactly?

Cheers

"Forward" is an adverb modifying the verb "look", giving the direction.
"To <whatever>" is a prepositional phrase used as an adverb modifying the
adverb "forward".

We don't seem to be coming to any conclusion. If it's the introduction of an adverb that prevents you from using an infinitive, I'd understand, but it's not. For example . . .
I hope, desperately, to walk to work tomorrow, seeing as the weather is so nice.
<subject> <verb> <adverb> <infinitive>
I look forward to walk to work tomorrow, seeings as the weather is so nice.
<subject> <verb> <adverb> <infinitive>

Both have the same structure, yet one makes sense while the other doesn't.

Anyway, I don't think we're going to resolve this, but thanks for all your replies.
Have a good day.

OK.

I was stumped, but reading what George prescribes, it's clearer to me now.

He's right.

I was stumped, but reading what George prescribes, it's clearer to me now.

He's right.

"I am looking forward to presenting tomorrow."

"Look forward to" is an idiom.

"I am hoping to present tomorrow."

If anyone else is interested, here's an answer I got from a different grammar site, which I think answers the question:
{Short Version}
What kind of complement (to-infinitive, bare infinitive, or an -ing form) goes with what verb is not something that can be determined by a grammatical rule. It is just a fact of English that it's 'look forward to + -ing' form, but hope/hoping/look/looking + to-infinitive, and that's pretty much all that can be said about it.

{Long version):
Look forward to
The traditional view is that look forward to is a phrasal verb which takes a gerund (-ing form) or a noun phrase as a complement. CGEL, however, takes the view that constructions that are traditionally called phrasal verbs 'despite their idiomatic interpretations, do not form syntactic constituents' and so they 'do not use the term "phrasal verb" in this grammar' (p. 274).
Instead, CGEL analyzes the phrase as belonging to 'Constructions containing verb + intransitive preposition idioms' (p. 286):
[44] iv verb - prep - transitive PP We look forward [to your visit].
Here 'Prep' stands for 'the intransitive preposition functioning as a complement of the verb.' 'PP' means 'prepositional phrase', in this case to your visit.
Note that according to CGEL, 'to' belongs with the complement (it's the head of the prepositional phrase), not with look forward; this is why they say that look forward to is not a syntactic constituent.
Hope/hoping
Hope is a catenative verb. Different catenative verbs take different kinds of non-finite clauses as complements (to-infinitives, bare infinitives, and/or present participles/gerunds), and there is no rule that can predict what kind of complement will be correct for any given catenative verb; hope happens to take a to-infinitive, and that's all that can be said about it (at least in the present state of our understanding of linguistics).
True, there are some tendencies in what catenative verb takes what kind of complement. However, these are tendencies only, and 'we could not, for example, predict that anticipate would take an -ing clause complement, and so on. Thus there is no getting away from the fact that the lexical entries for verbs must specify which kinds of complement they take and, where more than one is involved, the semantic differences (if any)' (IGE, pp. 210-211). Wiktionary has a list of catenative verbs grouped by what sort of complement they take.
Look/looking
By the way, I’m looking to present tomorrow is perfectly fine; see 1Bi, below.
Like hope, look is a catenative verb, and it is just a fact of the English language that it takes a to-infinitive as a complement. True, look does not appear on that Wiktionary list, but it does appear on a list in CGEL, in two incarnations (p. 1240): as type 1Bi and as type 1Bii, explained as follows (pp. 1227-1228)
1Bi: Kim looked to leave. (In Merriam-Webster, this is meaning 4b, 'to have in mind as an end' <looking to win back some lost profits>
1Bii: She looked to like it. (meaning more or less she seemed to like it)
The difference is that 1Bi has an ordinary subject, whereas 1Bii has a raised subject. That difference is explained in CGEL as follows (p. 1194):
(begin quote)
The semantic difference between the two kinds of subject can be illustrated with the verbs hope and seem:
[1] i Liz hoped to convince them. [ordinary subject]
ii Liz seemed to convince them. [raised subject]
In Liz is an ordinary subject in that it is an argument of the verb: hope denotes a psychological attitude on the part of someone to some situation (here Liz's attitude to the later, potential, situation where she convinces them). But in [ii] Liz is not an argument of seem. The meaning is something like "Seemingly, Liz convinced them"; seem has a modal meaning, serving to make [ii] weaker than the unmodalized Liz convinced them. Syntactically Liz is subject of seem, but semantically it relates only to the subordinate convince clause, not to seem. Liz in [ii] is then a raised subject: the verb that Liz relates to syntactically is higher in the constituent structure than the one it relates to semantically.

In [1i], Liz has two semantic roles, as experiencer of hope and as agent of convince; but in [ii], Liz has only one semantic role, as agent of convince. The difference is like that between [68i] and [68ii] of §1.7 (Pat persuaded Kim to travel by bus and Pat intended Kim to travel by bus), and we will again say that the missing subject of the non-finite clause has a controlled interpretation in [1i] and a raised interpretation in [1ii]. Verbs like seem which take a raised complement are called raising verbs.
(end quote)

I'm glad you found a satisfactory explanation. Thanks for posting it.

For me, the three key points are:

1) CGEL analyzes the phrase as belonging to 'Constructions containing
verb + intransitive preposition idioms'

iv verb - prep - transitive PP We look forward [to your visit].
Here 'Prep' stands for 'the intransitive preposition functioning as
a complement of the verb.' 'PP' means 'prepositional phrase', in
this case to your visit.

Note that according to CGEL, 'to' belongs with the complement (it's
the head of the prepositional phrase), not with look forward

2) Hope is a catenative verb. Different catenative verbs take
different kinds of non-finite clauses as complements . . . hope
happens to take a to-infinitive.

3) By the way, I’m looking to present tomorrow is perfectly fine.




(Now I have to go look up "catenative verb" and "bare infinitive".)