\nLongrightarrow

[Mohamed Babaali]

Does a long, negative, double (implication) arrow really not exist in Latex
(or amstex or whatever) ????????

I need a negated $\Longrightarrow$. I've tried $\nLongrightarrow$, but it
does not work.

It would be a pity that, among hundreds of useless symbols, this thing is
not supported.

Thanks.

[Brooks Moses]

Post by Mohamed Babaali
Does a long, negative, double (implication) arrow really not exist in Latex
(or amstex or whatever) ????????
I need a negated $\Longrightarrow$. I've tried $\nLongrightarrow$, but it
does not work.

Have you checked out the Comprehensive LaTeX Symbol list? It's readily
available in a variety of formats (including A4 or letter paper) at:
http://www.ctan.org/tex-archive/info/symbols/comprehensive/

I suspect you may want to pay particular attention to the part of that
document that describes how to build up a symbol out of a combination of
other symbols. If you end up needing to do that for this symbol in
particular, and you use it often, I'd recommend defining a
\nLongrightarrow function for the purpose.

Post by Mohamed Babaali
It would be a pity that, among hundreds of useless symbols, this thing is
not supported.

It is, I would think, a pity that some people appear fond of assuming
that symbols are useless merely because they do not personally know the
use of them. :)

As the symbol in question is particularly easy to contruct out of a
regular \Longrightarrow and a negation line, I can't see that it's
especially important to include explicitly.

- Brooks

[Mohamed Babaali]

Thanks for the tip on the comprehensive thing...

\def\nLongleftarrow{/\mkern-25mu\Longleftarrow} produces what I'm looking
for, except that
\nLongleftarrow and \Longleftarrow do not line up correctly in a vertical
array (\nLongleftarrow is shifted to the left). Is this the best way to
create a \nLongleftarrow???

Post by Brooks Moses
It is, I would think, a pity that some people appear fond of assuming
that symbols are useless merely because they do not personally know the
use of them. :)

I knew my last line would generate such a comment! But come on, who needs
\fatslash ????? Most of those symbols are not standard in any way, so they
do not even have a "use" for people to proudly "know" :)

I insist on (and am very much fond of) thinking that \nLongleftarrow should
be a standard symbol. Why is \nLeftarrow standard and not my \nLongleftarrow
?

Regards,

Post by Brooks Moses

Post by Mohamed Babaali
Does a long, negative, double (implication) arrow really not exist in Latex
(or amstex or whatever) ????????
I need a negated $\Longrightarrow$. I've tried $\nLongrightarrow$, but it
does not work.

Have you checked out the Comprehensive LaTeX Symbol list? It's readily
http://www.ctan.org/tex-archive/info/symbols/comprehensive/
I suspect you may want to pay particular attention to the part of that
document that describes how to build up a symbol out of a combination of
other symbols. If you end up needing to do that for this symbol in
particular, and you use it often, I'd recommend defining a
\nLongrightarrow function for the purpose.

Post by Mohamed Babaali
It would be a pity that, among hundreds of useless symbols, this thing is
not supported.

It is, I would think, a pity that some people appear fond of assuming
that symbols are useless merely because they do not personally know the
use of them. :)
As the symbol in question is particularly easy to contruct out of a
regular \Longrightarrow and a negation line, I can't see that it's
especially important to include explicitly.
- Brooks

[Mohamed Babaali]

And by the way, {\not\Longleftarrow} does not work: \Longleftarrow is a
"LONG" arrow, and the negation is not centered...

Post by Mohamed Babaali
Thanks for the tip on the comprehensive thing...
\def\nLongleftarrow{/\mkern-25mu\Longleftarrow} produces what I'm looking
for, except that
\nLongleftarrow and \Longleftarrow do not line up correctly in a vertical
array (\nLongleftarrow is shifted to the left). Is this the best way to
create a \nLongleftarrow???

Post by Brooks Moses
It is, I would think, a pity that some people appear fond of assuming
that symbols are useless merely because they do not personally know the
use of them. :)

I knew my last line would generate such a comment! But come on, who needs
\fatslash ????? Most of those symbols are not standard in any way, so they
do not even have a "use" for people to proudly "know" :)
I insist on (and am very much fond of) thinking that \nLongleftarrow should
be a standard symbol. Why is \nLeftarrow standard and not my

\nLongleftarrow

Post by Mohamed Babaali
?
Regards,

Post by Brooks Moses

Post by Mohamed Babaali
Does a long, negative, double (implication) arrow really not exist in

Latex

Post by Brooks Moses

Post by Mohamed Babaali
(or amstex or whatever) ????????
I need a negated $\Longrightarrow$. I've tried $\nLongrightarrow$, but

it

Post by Brooks Moses

Post by Mohamed Babaali
does not work.

Have you checked out the Comprehensive LaTeX Symbol list? It's readily
http://www.ctan.org/tex-archive/info/symbols/comprehensive/
I suspect you may want to pay particular attention to the part of that
document that describes how to build up a symbol out of a combination of
other symbols. If you end up needing to do that for this symbol in
particular, and you use it often, I'd recommend defining a
\nLongrightarrow function for the purpose.

Post by Mohamed Babaali
It would be a pity that, among hundreds of useless symbols, this thing

is

Post by Brooks Moses

Post by Mohamed Babaali
not supported.

It is, I would think, a pity that some people appear fond of assuming
that symbols are useless merely because they do not personally know the
use of them. :)
As the symbol in question is particularly easy to contruct out of a
regular \Longrightarrow and a negation line, I can't see that it's
especially important to include explicitly.
- Brooks

[Donald Arseneau]

Post by Mohamed Babaali
\def\nLongleftarrow{/\mkern-25mu\Longleftarrow} produces what I'm looking

Hmmm. I should get his macro included in the document:

%------------------------------------------------------------------------------
% Generic math-overlay macro: \moverlay{\backslash \cr /\cr \hbox{---}}
% (Yes, use \cr to separate items; this is for use in defining composite
% symbols, not for direct use in a document.)

\def\moverlay{\mathpalette\***@rlay}
\def\***@rlay#1#2{\leavevmode\vtop{%
\baselineskip\***@skip \lineskiplimit-\maxdimen
\ialign{\hfil$#1##$\hfil\cr#2\crcr}}}

Then:

\newcommand\nLongleftarrow{\mathrel{\moverlay{\Longleftarrow\cr /}}}

Donald Arseneau ***@triumf.ca

[Robin Fairbairns]

[brooks moses wrote]

Post by Brooks Moses
It is, I would think, a pity that some people appear fond of assuming
that symbols are useless merely because they do not personally know the
use of them. :)

I knew my last line would generate such a comment! But come on, who needs
\fatslash ????? Most of those symbols are not standard in any way, so they
do not even have a "use" for people to proudly "know" :)

until very recently there were (to all intents and purposes) no
standards of any sort for any but the most trivial maths symbols.

however, even with your interepretation of the word "standard", you
should remember that designing symbols takes time (and hence money):
the fact that someone has designed the symbol must surely mean it's in
regular use in publications in some area of mathematics that you and i
don't know of.

I insist on (and am very much fond of) thinking that \nLongleftarrow should
be a standard symbol. Why is \nLeftarrow standard and not my \nLongleftarrow
?

because no-one with the ability has previously seen the need to design
one. you'll probably find someone (who knows how: i'm not terribly
good at symbol construction) will come along soon and tell you how to
create a centred negation on a \Longleftarrow. don't despair ;-)

[Herbert Voss]

Post by Mohamed Babaali
Does a long, negative, double (implication) arrow really not exist in Latex
(or amstex or whatever) ????????
I need a negated $\Longrightarrow$. I've tried $\nLongrightarrow$, but it
does not work.

\documentclass{article}
\usepackage{amsmath}
\makeatletter
\newcommand{\xLeftarrow}[2][]{%
\***@arrow 0055{\Leftarrowfill@}{#1}{#2}%
}
\def\Leftarrowfill@{\arrowfill@\Leftarrow\Relbar\Relbar}
\newcommand{\xRightarrow}[2][]{%
\***@arrow 0055{\Rightarrowfill@}{#1}{#2}%
}
\def\Rightarrowfill@{\arrowfill@\Relbar\Relbar\Rightarrow}
\makeatother
\begin{document}
$\xRightarrow[under]{over}$
$\xLeftarrow[under]{over}$
\end{document}

Herbert

[Frank Mittelbach]

Post by Mohamed Babaali
Does a long, negative, double (implication) arrow really not exist in
Latex (or amstex or whatever) ????????
I need a negated $\Longrightarrow$. I've tried $\nLongrightarrow$, but it
does not work.
It would be a pity that, among hundreds of useless symbols, this thing is
not supported.
Thanks.

St. Mary Road Symbol font has all kind of arrow construction symbols
including \Longarrownot so

\Longarrownot\Longrightarrow

should give what you want and defining that as \nLongrightarrow shouldn't be
too difficult

frank