To have done is a perfect infinitive and having done is a perfect participle. I don't understand what you mean with "applied in writing". They are what I said in both writing and speech.
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To have done is a perfect infinitive and having done is a perfect participle. I don't understand what you mean with "applied in writing". They are what I said in both writing and speech.
CB
Kevin Dunnto have done and having done
As already noted, these are an infinitive and a participle. Place them in your speech or writing wherever and infinitive or participle is required. You make the choice on the basis of the governing expression that precedes it. Some expressions require an infinitive to complete them; others need a participle.
CJ