netspook wrote:Also I would like to ask - are there any rules which can help me to distinguish the preposition "to" (e.g.look forward to) from infinitive (e.g.to do ) ?
No rules, just experience and careful study of the context.
In the sentence below is the "to" preposition or infinitive ?
"But it was not to last."
1."to" is preposition and "last" is noun ?
No. The sentence would not make any sense. The word "last" can be a
noun: a last is a solid form in the shape of a foot, used by shoemakers.
verb: to last means to endure or continue for a period of time.
adjective: The last item in a list is the one which has no others following.
2 "to last" is infinitive ?
Yes, the infinitive of the verb "to last". See above.
The preposition "to" would usually be followed by a gerund or noun
I was looking forward to
seeing Joe after twenty years
I am looking forward to my holidays
I am writing a letter to Jim.
When the word "to" is used as part of the infinitive form of a verb, it is followed by that verb.
I am going to kill the weeds in my garden.
I like to sing in my bath.
People are slow to wake when they went to bed late the night before.