This is the infinitive form of the present perfect tense. Remember, we use the present perfect to describe something which has been (recently) completed and still has a bearing on present and/or future circumstances. Compare the following:

• I have recently returned from India. To have seen the Taj Mahal in the early morning sunlight will always be something I shall never forget.
  
  
• You went to Aberdeen last week, didn't you? ~ Yes, I did. ~ To have gone all the way to Aberdeen and yet not to have called on your mother-in-law is something I cannot understand.
  
  
• So, do you have any money left at all now? ~ No, I don't. ~ To have lost all your money betting on horses is irresponsible to say the least when you have a family to look after.

Using an infinitive clause as the subject of the sentence in this way is a little unusual in an informal style. It is the sort of statement you would make having reflected on something of importance or significance.

To have something done

Take care not to confuse to have done something with to have something done. This structure (have + object + past participle) is used to talk about arranging for other people to do things for us and has the same sort of meaning as a passive sentence. Compare the following:

• We had this piece of furniture made specially so that it fits into the corner. It was made by John Lawrence, the antique furniture restorer.
  
  
• Why did you take your car to the garage? ~ To have it serviced. ~ When my car needs to be serviced, I just hand it over to Michael.
  
  Note that in informal English, we sometimes talk about getting things done, rather than having them done:
  
  
• I must get my watch repaired. It's so inconvenient being without one.
  When are you going to get your hair cut? ~ I'm not going to get it cut. I'm going to let it grow.

Like must, have to expresses obligation. Sometimes it doesn't matter which one we use, but the main difference is that must expresses personal feelings and have to expresses obligation which is imposed. Compare the following:

• Is it really as late as that? I must go now / I have to go now.
  
  
• I really must phone my mum tonight. I haven't spoken to her for ages.
  
  
• I know you don't want to, but you'll have to speak to him. He's waiting for your call.
  
  
• I'm sorry I'm late. I had to finish some work before I could leave. (Notice there is no past or participial form of must.)
  
  
• Having to finish your homework before you're allowed to watch television is not fair.

have got to

Note that we sometimes use have got to in present tense form as an alternative to have to. Although have got to often expresses future obligation, there is no future form of this verb. It is not used to express past obligation either. For future and past tense forms, we have to use have to. Compare the following:

• Can't you come to Brighton with me on Saturday? ~ No, I've got to work on Saturday. ~ You had to work last Saturday too. Will you have to work the following Saturday as well?
  
  

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