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I remember reading about capitalized forms of some accent macros, such as \Hat, \Dot, and so on, and possibly their use was related to specific typographic corrections. I think it was in an AMSLaTeX-related document, but now I don't manage to find out where. (They don't seem to appear in amsldoc.pdf, and I thought I had seen them there).

I can indeed use them in a LaTeX document with the amsmath package (without specifying any \newcommand): no undefined-macro errors appear. But I can't really see any typographic difference from the lowercase \hat, \dot, etc in the pdf output.

What is the difference between these capitalized forms and the usual lowercase ones? and in which packages do they appear?

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    amsmath has \def\Hat{\hat} (and similar) so they are exactly the same. I have vague memories of the difference being a remnant of earlier version which has been kept for compatibility but I cannot confirm that.
    – campa
    Dec 21, 2020 at 15:22
  • @campa Thank you. So probably I had also seen them in an earlier version. What you say answers my question: there's no difference between them. Please feel free to post that as an answer.
    – pglpm
    Dec 21, 2020 at 15:24
  • @campa It seems indeed they appeared in version 1.2, 1995, to obtain better positioning for stacked accents.
    – pglpm
    Dec 21, 2020 at 15:30
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    My recollection is that in the old days ordinary "accents" could not be stacked, e.g. \dot{\hat{x}} would not work (or maybe just not look good, I do not remember) but with the uppercase versions it did, i.e. one had to use \Dot{\Hat{x}} or \Dot{\hat{x}}. This is no longer necessary.
    – user231225
    Dec 21, 2020 at 15:30

1 Answer 1

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From the implementation notes:

The commands \Hat, \Tilde, ..., are supported as synonyms of \hat, \tilde, ..., for backward compatibility.

The origins of this go back to the original AmS-TeX macro package which defined the capitalized versions with some additional ceremony beyond what the lowercase versions did but said ceremony is not necessary in LaTeX.

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    I believe that amsmath version 1 still had the distinction; the capitalized macros were necessary when stacking accents (like in AMS-TeX), but version 2 changed the code so the capitalized macros became superfluous.
    – egreg
    Dec 21, 2020 at 22:49

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