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then anytime a \MH/ command was given \eg{notseen} as a \arg{msg} or
\arg{msgs} argument,
it would substitute all messages that are not a member of the sequence
\eg{seen}.
That is,
\example refile notseen +new\endexample
does just that.
The value of the \entry{Sequence-Negation} entry in the profile can be
any string.
Hence,
experienced users of \MH/ do not use a word,
but rather a special character which their shell does not interpret
(users of the \pgm{CShell} use a single carat, \eg{`\^'},
while users of the Bourne shell use an exclamation-mark, \eg{`!'\/}).
This is because there is nothing to prevent a user of \MH/ from defining a
sequence with this string as its prefix,
if the string is nothing but letters and digits.
Obviously,
this could lead to confusing behavior
if the \entry{Sequence-Negation} entry leads \MH/ to believe that two
sequences are opposites, by virtue of their names differing by the prefix
string.
\subsubsection{The Previous Sequence}
Many times users find themselves issuing a series of commands on the same
sequences of messages.
If the user first defined these messages as a sequence,
then considerable typing may be saved.
If the user doesn't have this foresight,
\MH/ provides a handy way of remembering the \arg{msgs} or
\arg{msg} argument last given to a \MH/ command by the user.
If the entry \entry{Previous-Sequence} is defined in the \profile/ file,
then when the command finishes,
it will define the sequence(s) named in the value of this entry as being
defined as those messages that were specified.
Hence, a profile entry of
\example Previous-Sequence: pseq\endexample
directs any \MH/ command that accepts a \arg{msg} or \arg{msgs} argument to
define the sequence \eg{pseq} as those messages when it finishes.
More than one sequence name may be placed in this entry,
separated with spaces.
The one disadvantage of this approach
is that all \MH/ commands have to update the sequence information for
the folder each time they run
(although most commands read this information,
usually only \pgm{pick} and \pgm{mark} have to write this information out).
\section{Composition of Mail}
Two new facilities have been added to give the \MH/ user greater power in
composing and sending mail:
the {\it draft folder},
which allows a user to maintain a folder of message drafts;
and, {\it draft pushing},
which permits a user to \pgm{send} the current draft in the background.
\subsection{The Draft Folder}
The \pgm{comp}, \pgm{dist}, \pgm{forw}, and \pgm{repl} commands have two
hidden switches, \switch{draftfolder~+folder} and \switch{draftmessage~msg}.
If \switch{draftfolder~+folder} is used,
these commands are directed to construct a draft message in the indicated
folder.
If \switch{draftmessage~msg} is not used, it defaults to \arg{new}
(unless the user invokes \pgm{comp} with \switch{use},
in which case the default is \arg{cur}).
Hence, the user may have several message compositions in progress
simultaneously.
Now, all of the \MH/ tools are available on each of the user's message
drafts
(e.g., \pgm{show}, \pgm{scan}, \pgm{pick}, and so on).
If the folder does not exist,
the user is asked if it should be created (just like with \pgm{refile\/}).
Also,
the last draft message the user was composing is known as \arg{cur} in the
draft folder.
\par
Furthermore,
the \pgm{send} command has these switches as well.
Hence, from the shell,
the user can send off whatever drafts desired using the
standard \MH/ \arg{msgs} convention with \switch{draftmessage msgs}.
If no \arg{msgs} are given, it defaults to \arg{cur}.
\par
In addition,
all five programs have a \switch{nodraftfolder} switch,
which undoes the last occurance of \switch{draftfolder~folder}
(useful if the latter occurs in the user's \MH/ profile).
\par
If the user does not give the \switch{draftfolder~+folder} switch,
then all these commands act ``normally''.
Note that the \switch{draft} switch to \pgm{send} and \pgm{show}
still refers to the file called \eg{draft} in the user's \MH/
directory.
In the interests of economy of expression,
when using \pgm{comp} or \pgm{send},
the user needn't prefix the draft \arg{msg} or \arg{msgs} with
\switch{draftmessage}.
Both of these commands accept a \arg{file} or \arg{files} argument,
and they will, if given \switch{draftfolder~+folder} treat these arguments
as \arg{msg} or \arg{msgs}.%
\nfootnote{This may appear to be inconsistant, at first,
but it saves a lot of typing.}
Hence,
\example send -draftf +draft first\endexample
is the same as
\example send -draftf +draft -draftm first\endexample
\par
To make all this a bit more clear, here are some examples.
Let's assume that the following entries are in the \profile/ file:
\example
    comp: -draftfolder +draft\\
    dist: -draftfolder +draft\\
    forw: -draftfolder +draft\\
    repl: -draftfolder +draft\\
    sendf: -draftfolder +draft%
\endexample
Furthermore,
let's assume that the program \pgm{sendf} is a symbolic link in the user's 
\file{\$HOME/bin/} directory to \pgm{send}.
Then, any of the commands
\example
    comp\\
    dist\\
    forw\\
    repl%
\endexample
constructs the message draft in the \eg{draft} folder using the \arg{new}
message number.
Furthermore,
they each define \arg{cur} in this folder to be that message draft.
If the user were to use the \pgm{quit} option at \whatnow/ level,
then later on,
if no other draft composition was done,
the draft could be sent with simply
\example sendf\endexample
Or,
if more editing was required,
the draft could be edited with
\example comp -use\endexample
Instead,
if other drafts had been composed in the meantime,
so that this message draft was no longer known as \arg{cur} in the \eg{draft}
folder,
then the user could \pgm{scan} the folder to see which message draft in the
folder should be used for editing or sending.
Clever users could even employ \pgm{pick} to do the work:
\example
    comp -use \bq{pick +draft -to bug-mh}\\
\noalign{\leftline{or}}
    sendf \bq{pick +draft -to bug-mh}%
\endexample
Note that in the \pgm{comp} example,
the output from \pgm{pick} must resolve to a single message draft
(it makes no sense to talk about composing two or more drafts with one
invocation of \pgm{comp\/}).
In contrast,
in the \pgm{send} example,
as many message drafts as desired can appear,
since \pgm{send} doesn't mind sending more than one draft at a time.
\par
Note that the argument \switch{draftfolder~+folder} is not
included in the profile entry for \pgm{send},
since when \pgm{comp}, et. al., invoke \pgm{send} directly,
they supply \pgm{send} with the \unix/ pathname of the message draft,
and {\it not} a \arg{draftmessage~msg} argument.
As far as \pgm{send} is concerned,
a {\it draft folder} is not being used.
\par
It is important to realize that \MH/ treats the draft folder like a standard
\MH/ folder in nearly all respects.
There are two exceptions:
\underbar{first}
under no circumstancs will the \arg{draftfolder~folder} switch cause the
named folder to become the current folder.%
\nfootnote{Obviously,
if the folder appeared in the context of a standard \arg{+folder}
argument to an \MH/ program, as in
\example scan +draft\endexample
it might become the current folder, depending on the context changes of the
\MH/ program in question.}
\underbar{Second},
although conceptually \pgm{send} deletes the \arg{msgs} named in the draft
folder,
it does not call \entry{delete-prog} to perform the deletion.
\subsection{What Happens if the Draft Exists}
When the \pgm{comp}, \pgm{dist}, \pgm{forw}, and \pgm{repl} commands are
invoked and the draft you indicated already exists,
these programs will prompt the user for a reponse directing the program's
action.
In \mh4, the prompt is
\begingroup
    \smallertype
    \example
	``/usr/src/uci/mh/mhbox/draft'' exists; replace, list, or quit?%
    \endexample
\endgroup
The appropriate responses and their meanings are:
\smallskip
{\advance\leftskip by\parindent
\item{\underbar{replace}:} deletes the draft and starts afresh.
\item{\underbar{list}:} lists the draft.
\item{\underbar{quit}:} leaves the draft intact and exits.
\smallskip}
\noindent
In addition, if you specified \switch{draftfolder~folder} to the command,
then one other response will be accepted:
\smallskip
{\advance\leftskip by\parindent
\item{\underbar{new}:} finds a new draft,
just as if \switch{draftmessage~new} had been given.
\smallskip}
\noindent
Finally, the \pgm{comp} command will accept one more response:
\smallskip
{\advance\leftskip by\parindent
\item{\underbar{use}:} re-uses the draft,
just as if \switch{use} had been given.
\smallskip}
\subsection{The Push Option at\/{ }\whatnow/ Level}
The \pgm{comp}, \pgm{dist}, \pgm{forw}, and \pgm{repl} commands take
an additional option for the \whatnow/ query.
The \pgm{push} option, which must be spelled out fully,
directs the command to \pgm{send} the draft
in a special detached fashion,
with all normal output is discarded.
If \pgm{push} is used and the draft can not be sent,
then \MH/ will send the user a message,
indicating the name of the draft file,
and an explanation of the failure.
Although using \pgm{push} calls \man{send}(1),
the \pgm{send} command will consult the profile entry for \pgm{push}.
\par
The user can also invoke \pgm{send} from the shell with the \switch{push}
switch,
which makes \pgm{send} act like it had been \pgm{push\/}'d by one of the
composition commands.%
\nfootnote{Note that in this case,
\pgm{send} consults the profile entry for whatever name it was invoked as,
such as \pgm{sendf}.}
\par
The \pgm{send} program also has two other switches,
\switch{unique} and \switch{nounique}.
If \pgm{push\/}'d,
then the \switch{unique} switch tells \pgm{send} to rename the draft file to
a unique filename.
This allows the user to have several drafts being sent simultaneously