[Grammar] To think that he was my best friend!

[yuriya]

When I come across sentences like "To think that he was my best friend!", I get the general idea from the context. I have never given much thought before but I just got curious. Is it even grammatically right?

And am I right to interpret the above sentence as something like
(depending on its context used of course)

"How stupid I was to think that he was my best friend!"


Thank you for your kind help in advance!

 

[macanudo]

This is an 'infinitive phrase fragment' a type of fragment. It is technically incorrect, but you can use it in speech. You shouldn't use it in writing though.