typesetting of negative versus minus

Question

I've occasionally seen a negative (when a number is simply negative, not a subtraction), typeset as negative sign that's slightly skinnier and above the centre line of text. Is this proper notation for mathematics and how would one go about typesetting this in latex?

Edit

I believe that calculators were what happened to give me this idea, couldn't find it in any of my math books. Thank you all for the help, it's much appreciated.

Thank you 'Antal S-Z' for the photo link.

However, the question remains, how exactly would I typeset this?

Answer 1

My understanding is that a negative sign is the same as a minus sign, but the spacing is different since it's a unary operator rather than a binary operator. You can see this in TeX: $-x$ has different spacing from $y-x$:

I'm not sure I can answer your question about it being proper, but I'll say that I've never seen mathematics typeset with a raised, smaller negative sign. (But take that with a grain of salt because most, but not all, math I read is typeset with LaTeX.)

Answer 2

Here is a LuaLaTeX approach that discovers unary minuses automatically (but the \raisebox doesn't work for a reason I don't understand):

\documentclass{minimal}

\usepackage{luatextra}
\usepackage{xparse}

\makeatletter
\NewDocumentCommand{\raisedminus}{m}{%
  \raisebox{0.2em}{$\m@th#1{-}$}%
}
\makeatother

\newsavebox{\scriptraisedminus}
\sbox{\scriptraisedminus}{\raisedminus{\scriptstyle}}
\newsavebox{\scriptscriptraisedminus}
\sbox{\scriptscriptraisedminus}{\raisedminus{\scriptscriptstyle}}

\begin{luacode}
local unary_minus = node.new(15)
unary_minus.display = node.new(16, 0)
unary_minus.display.nucleus = node.new(32)
unary_minus.display.nucleus.list = node.copy_list(tex.getbox(\number\scriptraisedminus))
unary_minus.text = node.new(16, 0)
unary_minus.text.nucleus = node.new(32)
unary_minus.text.nucleus.list = node.copy_list(tex.getbox(\number\scriptraisedminus))
unary_minus.script = node.new(16, 0)
unary_minus.script.nucleus = node.new(32)
unary_minus.script.nucleus.list = node.copy_list(tex.getbox(\number\scriptscriptraisedminus))
unary_minus.scriptscript = node.new(16, 0)
unary_minus.scriptscript.nucleus = node.new(32)
unary_minus.scriptscript.nucleus.list = node.copy_list(tex.getbox(\number\scriptscriptraisedminus))

function is_bin_conv_to_ord(v, p)
  if not v or v.id \string~= 16 or v.subtype \string~= 4 then return false end
  if not p then return true end
  if p.id == 16 and ((p.subtype >= 1 and p.subtype <= 6) or p.subtype == 8) then return true end
  local n = v.next
  if q and q.id == 16 and (q.subtype == 5 or q.subtype == 7 or q.subtype == 8) then return true end
  return false
end

function replace_unary_minus(head, displaytype, need_penalties)
  local p = nil
  local v = head
  while v do
    if is_bin_conv_to_ord(v, p) then
      local n = v.nucleus
      if n and n.id == 31 and n.fam == 2 and n.char == 0 then
        node.insert_after(head, v, node.copy(unary_minus))
        head, w = node.remove(head, v)
      end
    end
    p = v
    v = v.next
  end
  return node.mlist_to_hlist(head, displaytype, need_penalties)
end

luatexbase.add_to_callback("mlist_to_hlist", replace_unary_minus, "replace_unary_minus")
\end{luacode}

\begin{document}

$-3 - 4$

\end{document}

Answer 3

Here is an example, but you still have to distinguish between unary and binary minus manually:

\documentclass{minimal}

\usepackage{xparse}

\makeatletter
\NewDocumentCommand{\raisedminus}{m}{%
  \raisebox{0.2em}{$\m@th#1{-}$}%
}
\NewDocumentCommand{\unaryminus}{}{%
  \mathbin{%
    \mathchoice{%
      \raisedminus\scriptstyle
    }{%
      \raisedminus\scriptstyle
    }{%
      \raisedminus\scriptscriptstyle
    }{%
      \raisedminus\scriptscriptstyle
    }%
  }%
}
\makeatother

\begin{document}

$\unaryminus 3 - 4$

\end{document}

Answer 4

If latex gives you a binary minus and you want the unary minus (i.e. negative), just add curly braces around the expression, e.g. change -x to {-x}. See post #4 at mathhelpforum

Answer 5

I'll throw in a few thoughts to answer the part "Is this proper notation for mathematics" of the question. First of all: No, it's not proper. One reason, as others have observed before me: It's just never used, except in school textbooks where they have to distiguish two different keys on the calculator keyboard. So, if you type a manual for a calculator, you can use Philipp's \unaryminus. (And otherwise you shouldn't use it.)

The second reason: Try to use the symbol in handwriting. Will you really manage to write it in a way that it is always clear which of two minus symbols is meant? At least I wouldn't. I think this is one of the reasons why in mathematics there is just this one minus sign.

What I can't answer is why they have two different keys on the calculator. Maybe it was for simplifying the programming in the early days, or it's for didactic reason; I don't know.