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<H2><A NAME="SECTION00663000000000000000"> </A> <A NAME="2132"> </A>
<BR>
DO Loops
</H2>
<P>
Loops<A NAME="2133"> </A> are supported in MIDAS procedures like the <TT>DO</TT> loops in
FORTRAN (but note that loops are always executed at least once):<BLOCKQUOTE>
<TT>!+ <BR>
! Example 9, MIDAS procedure exa9.prg <BR>
!+ <BR>
WRITE/KEYWORD N/I/1/1 0 </TT>! keywords serve as loop variables<TT>
<BR>
DO N = 1 6 2 </TT>! loop from N=1 until N<IMG
WIDTH="22" HEIGHT="39" ALIGN="MIDDLE" BORDER="0"
SRC="img131.gif"
ALT="$\leq$">6 in steps of 2<TT> <BR>
WRITE/OUT N = </TT><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img132.gif"
ALT="$\{$"><TT>N</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img133.gif"
ALT="$\}$"><TT> <BR>
ENDDO</TT></BLOCKQUOTE>A keyword of integer type (called N in our example) must be used to
store the loop variable. The parameters follow the standard FORTRAN conventions
with start (=1 in <TT>exa9.prg</TT>), end (=6) and in/decrement (=2) values
given as shown above. DO loops may be nested up to 8 levels
deep in a procedure. <BR>
<BR>
The command <TT>@@ exa9</TT> will yield<BLOCKQUOTE>
<TT>N = 0001 <BR>
N = 0003 <BR>
N = 0005 </TT></BLOCKQUOTE>Assume we have images <TT>imag0001.bdf</TT> to <TT>imag0100.bdf</TT> and want to add
successive pairs and store the results into images <TT>res0001.bdf</TT> to
<TT>res0050.bdf</TT>:<BLOCKQUOTE>
<TT>!+ <BR>
! Example 10, MIDAS procedure exa10.prg <BR>
!+ <BR>
DEFINE/PARAM P1 ? IMA "Enter root_name for input frames: " <BR>
DEFINE/PARAM P2 ? IMA "Enter root_name for output frames: " <BR>
DEFINE/MAXPAR 2 </TT>! max. 2 parameters expected<TT>
<BR>
SET/FORMAT I4 </TT>! we need 4 digits<TT>
<BR>
WRITE/KEYWORD N/I/1/1 0
<BR>
WRITE/KEYWORD NN/I/1/2 0,0 <BR>
! <BR>
DO N = 1 50 </TT>! default increment is 1 <TT> <BR>
NN(1) = 2*N <BR>
NN(2) = NN(1)-1 <BR>
COMPUTE/IMAGE </TT><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img134.gif"
ALT="$\{$"><TT>P2</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img135.gif"
ALT="$\}$"><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img136.gif"
ALT="$\{$"><TT>N</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img137.gif"
ALT="$\}$"><TT> = </TT><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img138.gif"
ALT="$\{$"><TT>P1</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img139.gif"
ALT="$\}$"><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img140.gif"
ALT="$\{$"><TT>NN(2)</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img141.gif"
ALT="$\}$"><TT>+</TT><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img142.gif"
ALT="$\{$"><TT>P1</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img143.gif"
ALT="$\}$"><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img144.gif"
ALT="$\{$"><TT>NN(1)</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img145.gif"
ALT="$\}$">! sum up<TT> <BR>
LOAD/IMAGE </TT><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img146.gif"
ALT="$\{$"><TT>P2</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img147.gif"
ALT="$\}$"><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img148.gif"
ALT="$\{$"><TT>N</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img149.gif"
ALT="$\}$">! display the result frame<TT> <BR>
ENDDO</TT></BLOCKQUOTE>Then, the MIDAS command <TT>@@ exa10 imag res</TT> will do the required task.
<P>
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<ADDRESS>
<I>Petra Nass</I>
<BR><I>1999-06-09</I>
</ADDRESS>
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