Forum: ell.stackexchange.com
Tags: <infinitives>
Title: "It's not a problem at all TO do that" vs. "It's not a problem at all do that" (without TO before do)
Question: Which of these is correct?     It's not a problem at all  TO do  that   vs.    It's not a problem at all  do  that (without TO before do)

Answers:
sents: text: It's not a problem at all TO do that.
text: You can imagine this question and answer: What is not a problem at all? -
text: "To do that".
text: But you cannot imagine this:
text: What is not a problem at all?
text: - "Do that."
text: (here, "do that" is a command , not an answer to this question) You can remodel your sentence thus: To do that is not a problem at all.
text: But it would be ungrammatical without to : Do that is not a problem at all.
text: (NOT OKAY)
text: Why?
text: Because "to do that" is what is called an " infinitive phrase ".
text: An infinitive phrase can be used as a noun phrase when it has the particle to .
text: That is, with the particle "to", we can put an equality sign between the phrase "to do that" and the noun "problem": "a rectangle" =
text: "a square" (both words are nouns) "to do that" =
text: "a problem" (both serve as nouns) [To do that] is not [a problem]
text: (we put "is" instead of "=" and added "not")
text: [It] is not [a problem][to do that].
text: (we added the pronoun "it".
text: A pro noun , speaking simply, is a word that is used as a stand-in for a noun .
text: In our case, such "noun" is [to do that])
answer_details: author: ell.stackexchange.com/users/2127/CowperKettle
score: 4
sents: text: Normally you could say: Could you go to the store for me?
text: (reply)
text: It's not a problem at all to do that.
text: It means there is no problem for "you" to go to the store.
text: The second phrase is not OK as is, but you could say: Do you mind if I answer the phone?
text: (reply)
text: It's not a problem at all, do that.
text: spoken with a pause between all and do .
text: This mean that you don't have any problem, but here you are telling someone (the person asking the question) to do something.
answer_details: author: ell.stackexchange.com/users/1423/user3169
score: 3
sents: text: You probably mean the first one.
text: They both could be correct (particularly if you add a bit of punctuation to the second one), but they mean different things.
text: It's not a problem at all to do that
text: This means that doing "that" is not a problem.
text: Depending on context it might be a bit stilted, another way to phrase it might be
text: "
text: Doing that isn't a problem at all." or
text: "That's not a problem at all."
text: But It's not a problem at all
text: do that ideally with the comma or semicolon:
text: It's not a problem at all, do that
text: It's not a problem at all; do that It means that's not a problem, go ahead and do it.
text: It's a compound sentence saying two things: "It's not a problem" and then the imperative (command)
text: "Do that.
text: "
text: In more formal writing you wouldn't combine it, but informally it's not uncommon.
answer_details: author: ell.stackexchange.com/users/8743/T.J. Crowder
score: 2
sents: text: It's not a problem at all to do that
text: vs it's not a problem at all do that.
text: I think the second sentence with the bare infinitive is grammatically incorrect.
text: As for the second sentence with "to infinitive", it will be more idiomatic if use -ing form after problem (problem + -ing form) in this context.
text: We can use to-infinitive when the noun "problem" means a question or matter involving difficulty for example.
text: we were given five problems to solve, we have many problems to deal with.
text: On the other hand, when you face difficulty (in) doing something, you usually use the -ing form after problem (problem + -ing form), for example, I am having a problem finishing my work, the only problem is finding a job, etc.
text: So it's more idiomatic if we say "It's no problem/not a problem at all doing that".
answer_details: author: ell.stackexchange.com/users/9259/Khan
score: 1
sents: text: The use of the bare infinitive is limited to special cases:1 Auxiliary verbs as will/
text: would + bare infinitive (future and conditional)2 Modal verbs +
text: bare infinitive as "I can do it".3 A very limited number of other cases where a bare infinitive can be used.
text: But after nouns you can't use a bare infinitive.
text: The normal thing is a to-infinitive or sometimes of + gerund.
answer_details: author: ell.stackexchange.com/users/4159/rogermue
score: 1

Summary of the answers:
The sentence with the bare infinitive, wirthout "to" is grammatically incorrect, so you would say "It's not a problem at all TO do that".   However, it is more idiomatic to say "It's no problem/not a problem at all doing that".
The second sentence is grammatically incorrect. You sould say it's not a problem at all to do that/it's no problem.