It's not a problem at all TO do that.
You can imagine this question and answer: What is not a problem at all? -
"To do that".
But you cannot imagine this:
What is not a problem at all?
- "Do that."
(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.
But it would be ungrammatical without to : Do that is not a problem at all.
(NOT OKAY)
Why?
Because "to do that" is what is called an " infinitive phrase ".
An infinitive phrase can be used as a noun phrase when it has the particle to .
That is, with the particle "to", we can put an equality sign between the phrase "to do that" and the noun "problem": "a rectangle" =
"a square" (both words are nouns) "to do that" =
"a problem" (both serve as nouns) [To do that] is not [a problem]
(we put "is" instead of "=" and added "not")
[It] is not [a problem][to do that].
(we added the pronoun "it".
A pro noun , speaking simply, is a word that is used as a stand-in for a noun .
In our case, such "noun" is [to do that])
ell.stackexchange.com/users/2127/CowperKettle
Normally you could say: Could you go to the store for me?
(reply)
It's not a problem at all to do that.
It means there is no problem for "you" to go to the store.
The second phrase is not OK as is, but you could say: Do you mind if I answer the phone?
(reply)
It's not a problem at all, do that.
spoken with a pause between all and do .
This mean that you don't have any problem, but here you are telling someone (the person asking the question) to do something.
ell.stackexchange.com/users/1423/user3169
You probably mean the first one.
They both could be correct (particularly if you add a bit of punctuation to the second one), but they mean different things.
It's not a problem at all to do that
This means that doing "that" is not a problem.
Depending on context it might be a bit stilted, another way to phrase it might be
"
Doing that isn't a problem at all." or
"That's not a problem at all."
But It's not a problem at all
do that ideally with the comma or semicolon:
It's not a problem at all, do that
It's not a problem at all; do that It means that's not a problem, go ahead and do it.
It's a compound sentence saying two things: "It's not a problem" and then the imperative (command)
"Do that.
"
In more formal writing you wouldn't combine it, but informally it's not uncommon.
ell.stackexchange.com/users/8743/T.J. Crowder
It's not a problem at all to do that
vs it's not a problem at all do that.
I think the second sentence with the bare infinitive is grammatically incorrect.
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.
We can use to-infinitive when the noun "problem" means a question or matter involving difficulty for example.
we were given five problems to solve, we have many problems to deal with.
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.
So it's more idiomatic if we say "It's no problem/not a problem at all doing that".
ell.stackexchange.com/users/9259/Khan
The use of the bare infinitive is limited to special cases:1 Auxiliary verbs as will/
would + bare infinitive (future and conditional)2 Modal verbs +
bare infinitive as "I can do it".3 A very limited number of other cases where a bare infinitive can be used.
But after nouns you can't use a bare infinitive.
The normal thing is a to-infinitive or sometimes of + gerund.
ell.stackexchange.com/users/4159/rogermue
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)
"It's not a problem at all TO do that" vs. "It's not a problem at all do that" (without TO before do)
ell.stackexchange.com
<infinitives>
ell.stackexchange.com/questions/46471
ell.stackexchange.com/users/12430/Judicious Allure
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.
The second sentence is grammatically incorrect. You sould say it's not a problem at all to do that/it's no problem.