IF_THEN - Conditional execution of operations (Scripting operation)

PURPOSE

Allow conditional execution of sections of the SPIDER operation stream, depending on the logical value of an expression. Modeled after the FORTRAN 'IF...ELSEIF...ELSE...ENDIF'.

SEE ALSO

ELSEIF_THEN	[Conditional execution of operations (Scripting operation)]
ELSE	[Conditional execution of operations (Scripting operation)]
IF	[Conditional expression execution (Scripting operation)]
IF_GOTO	[Conditional jump (Scripting operation)]

USAGE

.OPERATION: IF(<EXP>.<LC>.<EXP>) THEN

~~~~~~~

~~~~~~~

ENDIF

Where:

1. <EXP> is an expression
2. <LC> is a logical comparator. The following comparators are allowed:

EQ    Equal

NE    Not equal

GT    Greater

GE    Greater/equal

LT    Less

LE    Less/equal

NOTES

1. EXAMPLES:

   IF([ysize].GE.15) THEN

   AC

   input001

   output001

   ENDIF

   IF([ysize].LT.15) THEN

   AC

   input001

   output001

   ELSEIF ([ysize].LT.150) THEN

   AC

   input001

   output002

   ELSE

   AC

   input001

   output003

   ENDIF

2. Nesting of IF_THEN..ELSE...ENDIF is limited to MAXPRC levels. See: CMLIMIT.INC for current value of MAXPRC.

3. For every 'IF_THEN' there must be a closing ENDIF!

4. There is no '.AND.' comparator.

5. The operation 'ELSEIF' was not available prior to SPIDER release 15.0.

6. Implemented by: ArDean Leith

SUBROUTINES

LOGIFQ

CALLER

SPIDER