To-infinitives are used in several structures. Here is a quick overview of them.
To-infinitives can be used after adjectives expressing ideas such as desire or emotion.
We were happy to see him.
She is afraid to talk.
He is eager to join the army.
I will be happy to accept your invitation.
He was anxious to meet you.
They are impatient to leave.
It + be + adjective + of + noun/pronoun + to-infinitive
The adjectives that are commonly used in this pattern are: good, kind, generous, stupid, unwise, wrong, brave, politely, silly, wicked, cruel, foolish, wise, nice, careless etc.
It is kind of you to help us.
It was foolish of me to lend him money.
It was clever of you to solve this puzzle.
It is wicked of her to do such things.
It was careless of you to make that mistake.
It is unwise of him to drink too much.
To-infinitives are words like difficult, easy, hard, impossible etc.
This book is easy to understand.
This carpet is difficult to wash.
Your actions are impossible to justify.
This food is difficult to swallow.
This medicine is pleasant to taste.
His speech was difficult to understand.
It + be + adjective + to-infinitive
It is easy to learn English.
It is difficult to get a job.
It is cruel to treat animals in that way.
It was impossible to win.
It is hard to get noticed.