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<H2><A NAME="SECTION00667000000000000000"> </A><A NAME="2361"> </A>
<BR>
Interrupting Procedures
</H2>
<P>
Sometimes, it may be necessary to interrupt the execution of procedures.
One way to do this is via the command <TT>INQUIRE/KEYWORD</TT> which was already
discussed before; depending upon the user input the procedure could continue or
stop. But while the procedure is waiting for input, MIDAS is blocked,
no other command can be executed.
<BR>
With the command <TT>PAUSE</TT> a procedure is stopped and saved; MIDAS returns to
the interactive level and you can execute any other command. To resume the
stopped procedure at a later time, enter <TT>CONTINUE</TT>. Then, the procedure
continues with the next command after the <TT>PAUSE</TT> line.
Only one procedure can be in the <TT>`PAUSEd'</TT> state at a time, in other
words it is not possible to stop and save several procedures together.
<BR>
As an example, consider the case where after some tricky operations on an image
you want to get a grayscale copy of the result on a Postscript Laser printer.
Since the grayscale plot is quite a time consuming operation you want to make
sure that the frame
is really o.k. before sending that job to the printer queue.
<P>
<BLOCKQUOTE>
<TT>!+ <BR>
! Example 17, MIDAS procedure exa17.prg <BR>
!+ <BR>
DEFINE/PARAM P1 ? IMA "Enter input frame: " <BR>
DEFINE/PARAM P2 ? IMA "Enter output frame: " <BR>
DEFINE/MAXPAR 2 </TT>! max. 2 parameters expected<TT>
<BR>
WRITE/KEYWORD IN_A </TT><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img172.gif"
ALT="$\{$"><TT>P1</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img173.gif"
ALT="$\}$"><TT> <BR>
DEFINE/LOCAL MYRESULT/C/1/80 </TT><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img174.gif"
ALT="$\{$"><TT>P2</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img175.gif"
ALT="$\}$"><TT> <BR>
RUN tricky.exe <BR>
PAUSE <BR>
! <BR>
INQUIRE/KEYWORD INPUTC "Result frame o.k.? Enter YES or NO: "
<BR>
IF INPUTC(1:1) .EQ. "Y" THEN <BR>
ASSIGN/DISPLAY LASER <BR>
LOAD/IMAGE </TT><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img176.gif"
ALT="$\{$"><TT>MYRESULT</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img177.gif"
ALT="$\}$"><TT> <BR>
ENDIF <BR></TT></BLOCKQUOTE> <BR>
With <TT>@@ exa17 venus jupiter</TT> the procedure will start the program
<TT>tricky</TT>
to operate on <TT>venus.bdf</TT> and produce the frame <TT>jupiter.bdf</TT>,
and then it will stop. Now, you can check the
result by e.g. calculating the statistics of <TT>jupiter.bdf</TT> or simply
displaying it. Then, resume the procedure via <TT>CONTINUE</TT>
and type <TT>YES</TT> if you are satisfied with the result and want the hardcopy
or <TT>NO</TT> if not.
<BR>
Note also, that we used a local keyword to hold the name of the result frame
and not the usual keyword <TT>OUT_A</TT>. Thus, we are sure that the result
name is not accidentally overwritten by another command which also uses
<TT>OUT_A</TT>.
<P>
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<ADDRESS>
<I>Petra Nass</I>
<BR><I>1999-06-09</I>
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