Is postscan the same as scan but with the first element dropped?

[eddiemundo]

I'm not sure since the implementation of scan and postscan are different looking.

[shlok]

Yes (if I understand you correctly). postscan drops the extraction of the initial fold state, but scan doesn't. (In practice, I have only used postscan because that simply yields an output for each input, whereas scan yields this one extra thing in the beginning.)