Re: Superscripts

From: Hans Aberg (
Date: Thu Nov 03 2005 - 11:37:34 CST

  • Next message: Philippe Verdy: "Re: Superscripts (was Re: Roman Numerals (was Re: Improper grounds for rejection of proposal N2677))"

    On 2 Nov 2005, at 17:44, Guy Steele wrote:

    > On Nov 2, 2005, at 1:39 AM, Jukka K. Korpela wrote:
    >> ... Incidentally, when exponentiation is to be expressed
    >> compactly in plain text, then I think UPWARDS ARROW U+2191 would
    >> be a better symbol than circumflex ^ (which was originally taken
    >> into use in exponential expressions since it can be imagined to be
    >> a simulation of an upwards arrow).
    > Agreed. I note, however, that ASCII originally (1963) did have an
    > "upwards arrow"
    > character, and a left arrow also. I well remember using Teletype
    > Model 33
    > terminals with these characters. There were programming languages
    > in the 1960s that used left arrow for assignment and/or up arrow for
    > exponentiation. (Digital Equipment Corporation's FOCAL languages, for
    > example, which ran on their PDP-8 computers, used = for assignment
    > but used up arrow for exponentiation.) When ASCII was revised
    > in 1967, the up arrow was replaced with the circumflex and the
    > left arrow with an underscore.

    This is mentioned at

    As for the superscript discussion, you need to separate a superscript
    character glyph, use to give an explicit name to the operator
    represented by superscripting, and superscripting indicated name
    implicit by raising the following or preceding symbol(s). The former
    case does not have so frequent use in math, but sometimes it does,
    for example in the case of exponentiation of the Church natural
    number functionals. In that case, the TeX \uparrow, which corresponds
    to ↑ (UPWARDS ARROW U+2191) seems natural, in part because, there
    appears to be not much use of an inline arrow in math, so this is a
    seemingly free symbol to use.

    Note however, though there are strong traditions of symbol use in
    math, there are no fixed standards. So another mathematician may well
    decide to use another symbol for explicit superscripting. This might
    happen if the upwards arrow needs to be given a better use. And one
    may use another symbol for implicit superscripting. And the math
    usage varies between areas, so what is used in math may not be
    convenient in computer science.

       Hans Aberg

    This archive was generated by hypermail 2.1.5 : Thu Nov 03 2005 - 12:18:29 CST