Sophie: eso-midas-doc-13SEPpl1.2-3.mga5 i586

eso-midas-doc-13SEPpl1.2-3.mga5.i586.rpm

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<H2><A NAME="SECTION00664000000000000000">&#160;</A><A NAME="2156">&#160;</A>
<BR>
Local Keywords
</H2> 

<P>
Because keywords are implemented as a global data structure, different MIDAS
procedures can access the same keyword. This useful feature can cause problems,
however, if these keywords just serve as local, temporary variables like the
<TT>DO</TT> variables. Consider the procedures below:<BLOCKQUOTE>
<TT>!+ <BR>
  ! Example 11, MIDAS procedure exa11.prg <BR>
  !+ <BR>
WRITE/KEYWORD N/I/1/1 0
<BR>
DO N = 1 10 <BR>
     @@ test <BR>
ENDDO</TT>
<TT>!+ <BR>
  ! MIDAS procedure test.prg <BR>
  !+ <BR>
WRITE/KEYWORD N/I/1/1 0
<BR>
DO N = 1 12 <BR>
WRITE/KEYWORD INPUTI/I/12/1 </TT><IMG
 WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
 SRC="img150.gif"
 ALT="$\{$"><TT>N</TT><IMG
 WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
 SRC="img151.gif"
 ALT="$\}$"><TT> <BR>
ENDDO</TT></BLOCKQUOTE>Executing <TT>@@ exa11</TT> will give some unexpected results, since both 
procedures access the same integer keyword N as a common variable.
<BR>
<BR>
Therefore, procedures should use <I>local</I> keywords for DO loops <A NAME="2164">&#160;</A>and internal
working storage. Local keywords are defined inside a MIDAS procedure via the
command <TT>DEFINE/LOCAL</TT>. 
They are only known inside the procedure where they are defined (if the
<TT>lower_levels_flag</TT> is set, they are also defined
in all procedures called from this procedure).
Local keywords <A NAME="2167">&#160;</A>may have the same name as an existing global keyword (except the
system keyword names as stored in <TT>MID_MONIT:syskeys.dat</TT>) or local
keyword of any other procedure, since local keywords are searched
before the global ones.
The above example will work, if modified as follows: <BLOCKQUOTE>
<TT>!+ <BR>
  ! Example 12, MIDAS procedure exa12.prg <BR>
  !+ <BR>
DEFINE/LOCAL N/I/1/1 0 <BR>
DO N = 1 10 <BR>
      @@ test <BR>
ENDDO <BR></TT>
<TT>!+ <BR>
  ! MIDAS procedure test.prg <BR>
  !+ <BR>
DEFINE/LOCAL N/I/1/1 0 <BR>
DO N = 1 12 <BR>
WRITE/KEYWORD INPUTI/I/12/1 </TT><IMG
 WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
 SRC="img152.gif"
 ALT="$\{$"><TT>N</TT><IMG
 WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
 SRC="img153.gif"
 ALT="$\}$"><TT> <BR>
ENDDO</TT></BLOCKQUOTE>Local keywords are deleted when returning to the next higher level
at the end of a procedure.<BLOCKQUOTE>
<DIV ALIGN="CENTER">
<B>Note</DIV>
<I>Always provide all initial values to a keyword. For example,
<BR>
<TT>define/local lola/r/1/6 0</TT>
usually works as intended, i.e. all elements of keyword <TT>lola</TT> are filled
   with 0, but depending upon the computer and operating system the contents
   of lola(2,...,6) may be unpredictable. So, use
<BR>
<TT>define/local lola/r/1/6 0 all</TT>
   in order to fill all elements of keyword <TT>lola</TT> with 0.</I></B></BLOCKQUOTE><HR>
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<ADDRESS>
<I>Petra Nass</I>
<BR><I>1999-06-09</I>
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