1.3 Experimental Software

 By default, the experimental software library is not included in your ``search path'' (the list of directories in which IDL searches for the procedures you invoke). You may compile experimental procedures individually, or you may simply add the experimental directory to your search path. To do the latter, type EXPLIB,1  at the IUE_IDL> prompt and hit return. This places the experimental library ahead of the standard library in the search path. Experimental versions of procedures will now be accessed instead of standard versions. (Note that if you have already been using the standard version of a routine during the current session, it is already compiled, and IDL will not attempt to search for it a second time regardless of what you have done to the search path.)

You may use the EXPLIB routine to remove the experimental library from your search path. (Note that any experimental routine you have already accessed in the current session remains compiled.) Type EXPLIB,-1 to do this. If you type EXPLIB,0 you will be told whether or not the experimental library is already included in your search path.

A more powerful routine was recently written for manipulating the IDL search path called MPATH. MPATH will allow any directory to be added anywhere in the search path. It will also display the entire search path in an easy to read format by simply typing MPATH,0 . (You can also look at the search path directly by typing print,!path, but this may require examining a long and possibly confusing string of directories.)

As an example of compiling experimental routines, suppose the experimental library contains four procedures a, b, c, and d. Let us assume that a is a completely new procedure, and that b, c and d are new versions of standard procedures.

1. You enter IDL and execute d at least once.
   
   
2. You try to execute a but get an error because IDL cannot find a in any of the directories in its search path (or in your current directory).
   
   
3. You realize that a is an experimental procedure, so you type EXPLIB,1 to add the experimental library to your search path. Now you use procedure a with no problem.
   
   
4. You then also execute procedure b, thus compiling the experimental version of b.
   
   
5. You also want to run c, but you prefer to run the standard version of it. You remove the experimental library from your search path by typing EXPLIB,-1 and then execute c.

Which version of each procedure will you be using if you execute them all now?

a The experimental version.

b The experimental version.

c The standard version.

d The standard version.

To execute any other version you must compile it explicitly with the .RUN command.

To see what's in the experimental directory, you may type SPAWN,'dir '+!iuer.expr or $dir explib: .pro if your operating system supports spawns. If you can not spawn (e.g., on MACs), you can use the DIRLIST command, (e.g., DIRLIST,!iuer.expr+'*.pro' ).

To compile an individual experimental routine, type .RUN EXPLIB: followed by the procedure name. For example, to compile STARFIT from the experimental library, type .RUN EXPLIB:STARFIT. After the procedure has been compiled (you will see the IUE_IDL> prompt again), type the procedure call statement to execute the procedure. The EXPLIB logical is defined on the IUE alpha. If you have the software installed on your own machine, and the machine's operating system supports logicals, it may be defined also. Note that not all platforms support logicals.