Getting help

program names, file names
variable names
prompts, commands, program code

• ?


• dl


• Function keys

?

There are several ways to get help in IDL. One way is to type a question mark at the prompt:

IDLprompt> ?

This launches a browser with the IDL online help. It works much like an internet browser, such as Netscape or MSIE. The browser is pretty good at general help about IDL and specific help about programs that come with the IDL distribution, but it won't help with software written locally.

dl

Warning: dl doesn't work in a text-only IDL session. In that case, use doc_library instead of dl---they work the same way, but dl needs to be able to launch GUIs.

For help on home-grown software, you can use the dl command to look at documentation. If a program has documentation, dl will display it in a scrollable GUI (graphical user interface). Just provide the name of the function or procedure:

IDLprompt> dl, 'progname'

IDL will then look for a file named progname.pro in the directories listed in your !path . If it finds the file, and if the file is documented, the documentation will appear in the GUI. If it doesn't find the file, or if there's no documentation, it'll open an empty GUI.

A note about documentation regards the way calling sequence is specified. Try looking at the documentation for v.pro:

IDLprompt> dl, 'v'

The calling sequence section of the documentation is intended to indicate (almost) precisely what the user should type at the IDL prompt to correctly run the program. In the documentation, some of the parameters may be in square brackets. This means that those arguments are optional and may be omitted. Read the documentation carefully.

Function keys

The startup file (the one with graphics) defines a few special functions associated with the first three function keys. Hitting F1 will give open a scrollable GUI showing information about the current state of the IDL environment, including the program level and information about the local variables. If not at the main level, the GUI will indicate the current program level, the full path name of the source code at whose level the IDL session is currently working, and the line number of that source code file where the interpretter is currently stopped.

Hitting F2 will give a list of the currently compiled procedures and functions, as well as the full pathname of the source code for each. Hitting F3 gives a similar list, but instead of the file name, it gives a list of the expected arguments for each program. Expected keywords are in capital letters.