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<H2><A NAME="SECTION00666000000000000000"> </A><A NAME="2265"> </A>
<BR>
Special Functions
</H2>
<P>
Special functions may be used with the command <TT>COMPUTE/KEYWORD</TT>.
The currently supported functions are listed in the following tables
(on the next pages). Note, that <I>arg1, arg2</I>
may either be the name of a keyword, the contents of which are used, or
a constant. Character constants have to be enclosed in double quotes to
distinguish them from a keyword name.
On-line help for these functions is available via <TT>HELP COMPUTE/KEYWORD</TT>.
<P>
<BR>
<DIV ALIGN="CENTER"><A NAME="2320"> </A>
<TABLE>
<CAPTION><STRONG>Table 3.2:</STRONG>
Special Functions available for operations on keywords</CAPTION>
<TR><TD>
<DIV ALIGN="CENTER">
<TABLE CELLPADDING=3 BORDER="1" ALIGN="CENTER">
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><B> Command</B></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><B> Description</B></TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$ABS(<I> arg1</I>) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns the absolute value of
integer/real/double
<I> arg1</I> as integer/real/double</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$EXIST(<I> arg1</I>) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns 1 or 0, if
file <I> arg1</I> exists or not</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$EXISTD(<I> arg1</I>,<I> arg2</I>)
</TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns 1 or 0, if
descriptor <I> arg2</I> of frame
<I> arg1</I> exists or not</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$EXISTK(<I> arg1</I>) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns 1 or 0, if
keyword <I> arg1</I> exists or not</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$EXISTC(<I> arg1</I>,<I> arg2</I>)
</TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns the number of the column
specified in <I> arg2</I> of the table
<I> arg1</I>;
returns -2 or -1, if table <I> arg1</I> or
column <I> arg2</I> doesn't exist</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$FILTYP(<I> arg1</I>,<I> arg2</I>)
</TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns a type_no for file in <I> arg1</I>,
if the file name does not include a file type,
the type definition in <I> arg2</I> is appended
to the file name</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$INDEX(<I> arg1</I>,<I> arg2</I>)
</TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns index of string <I> arg2</I> in
string <I> arg1</I> as integer value (same as
function INDEX of FORTRAN 77, i.e. first
position is 1 (not 0))</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$INDEXB(<I> arg1</I>,<I> arg2</I>)
</TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>same as <TT> M$INDEX</TT> but search is done
backwards, starting at the end of the string</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$LEN(<I> arg1</I>) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns length of string <I> arg1</I>
until the first blank or end of string,
e.g. for argument "abcd" result=4
and for "abc de" result=3</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$STRLEN(<I> arg1</I>) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns `true' string length of <I> arg1</I>
e.g. for argument "abcd" result=4
for "abc de" result=6; if the string contains
only blanks, 0 will be returned</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$NINT(<I> arg1</I>) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns nearest integer of real/double
<I> arg1</I></TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$SYMBOL(<I> arg1</I>) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns the translation of Unix environment
variable <I> arg1</I> (or DCL symbol in VMS)
as a character string</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$LOWER(<I> arg1</I>) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns character string <I> arg1</I> in lower
case</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$UPPER(<I> arg1</I>) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns character string <I> arg1</I> in upper
case</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$TSTNO(<I> arg1</I>) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns 1 or 0, if string
<I> arg1</I> is a number or not</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$TIME() </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns current date and time as string of
30 characters (as given by the host system)</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$TIME(1) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns current date and time as string in
the form</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1> </TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT> yyyy-mm-dd</TT></TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$SECS() </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns the current time as no. of seconds
elapsed since 1st Jan. 1970 (as an integer)</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$AGL(<I> arg1</I>) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns contents of AGL definition file
<TT> agldevices.dat</TT> related to <I> arg1</I>
as an ASCII string</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$LN(arg1) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns natural logarithm of real/double
<I> arg1</I></TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$LOG(arg1) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns base-10 logarithm of real/double
<I> arg1</I></TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$EXP(arg1) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns exponential of real/double <I> arg1</I>
(base e)</TD>
</TR>
</TABLE></DIV>
<A NAME="special-functions-available-for-operations-on-keywords"> </A></TD></TR>
</TABLE>
</DIV>
<BR>
<P>
<BR>
<DIV ALIGN="CENTER"><A NAME="2339"> </A>
<TABLE>
<CAPTION><STRONG>Table 3.3:</STRONG>
Special Functions available for operations on keywords - cont.</CAPTION>
<TR><TD>
<DIV ALIGN="CENTER">
<TABLE CELLPADDING=3 BORDER="1" ALIGN="CENTER">
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><B> Command</B></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><B> Description</B></TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$SIN(arg1) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns sine of real/double angle <I> arg1</I>
(angle in degrees)</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$COS(arg1) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns cosine of real/double angle <I> arg1</I>
(angle in degrees)</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$TAN(arg1) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns tangent of real/double angle
<I> arg1</I> (angle in degrees)</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$ASIN(arg1) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns arcsine of real/double <I> arg1</I>
in degrees</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$ACOS(arg1) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns arccosine of real/double <I> arg1</I>
in degrees</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$ATAN(arg1) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns arctangent of real/double <I> arg1</I>
in degrees</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$SQRT(arg1) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns square root of real/double
<I> arg1</I></TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$VALUE(imag[x,y,z]) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns a pixel of image <I> imag</I>
as real value</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$VALUE(imag,dscr) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns an element of descr <I> dscr</I> of
frame <I> imag</I>
according to the descriptor type</TD>
</TR>
<TR><TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1><TT>M$VALUE(tbl,col,row) </TT></TD>
<TD ALIGN="LEFT" VALIGN="TOP" WIDTH=1>returns a single element of table <I> tbl</I>
in column <I> col</I> and row <I> row</I>
according to the column type</TD>
</TR>
</TABLE></DIV>
<A NAME="special-functions-available-for-operations-on-keywords"> </A></TD></TR>
</TABLE>
</DIV>
<BR>
<BR>
<BR>
<BR>
<BR>
Note, that the <TT>M$VALUE</TT> function is different from all other functions:
<BR>
Firstly it has a variable no. of arguments and secondly,
because its operands are not keyword names (or constants) but the real names
of images and tables.
<BR>
<BR>
As an example we want to to display the header of a FITS file stored on disk
(without converting the data), the FITS file name may be entered with or
without the file extension <TT>.mt</TT>;
if not given we append the type inside the procedure:<BLOCKQUOTE>
<TT>!+ <BR>
! Example 16, MIDAS procedure exa16.prg <BR>
!+ <BR>
DEFINE/PARAM P1 ? ? "Enter FITS file name:" <BR>
! <BR>
DEFINE/LOCAL INA/C/1/80 " " all
</TT>! that fills all elements of INA with blanks<TT> <BR>
DEFINE/LOCAL K/I/1/2 0,0 <BR>
! <BR>
K = M$INDEX(P1,".mt") </TT>! test, if type of FITS file entered<TT> <BR>
IF K .LT. 2 THEN <BR>
WRITE/KEYW INA </TT><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img162.gif"
ALT="$\{$"><TT>P1</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img163.gif"
ALT="$\}$"><TT>.mt
</TT>! if not, append type<TT> <BR>
ELSE <BR>
WRITE/KEYW INA </TT><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img164.gif"
ALT="$\{$"><TT>P1</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img165.gif"
ALT="$\}$">! if yes, no need to append type<TT> <BR>
ENDIF <BR>
INTAPE/FITS 1 midd </TT><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img166.gif"
ALT="$\{$"><TT>ina</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img167.gif"
ALT="$\}$"><TT> fnn | $more <BR>
! </TT>but if we want to save the no. of axes of the FITS file<TT>
<BR>
! </TT>we do not use the keyword name INA but it's contents<TT>
<BR>
K = M$VALUE(</TT><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img168.gif"
ALT="$\{$"><TT>ina</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img169.gif"
ALT="$\}$"><TT>,naxis) <BR>
WRITE/OUT we have </TT><IMG
WIDTH="17" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img170.gif"
ALT="$\{$"><TT>K</TT><IMG
WIDTH="16" HEIGHT="44" ALIGN="MIDDLE" BORDER="0"
SRC="img171.gif"
ALT="$\}$"><TT> axes</TT></BLOCKQUOTE>The MIDAS commands <TT>@@ exa16 test</TT> as well as <TT>@@ exa16 test.mt</TT>
will both display the header of the FITS file <TT>test.mt</TT>.
Note, that this procedure will display the header in a user friendly way, i.e.
one screen at a time (and only work for Unix).
<BR>
One of the MIDAS verification procedures, <TT>verify3.prg</TT>
shows the usage of all currently available
functions. Enter <TT>@ vericopy</TT> to copy this procedure into your current
directory (also the usage of <TT>verify3</TT> will be shown then).
<P>
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<ADDRESS>
<I>Petra Nass</I>
<BR><I>1999-06-09</I>
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