... party¹

An extensive list of third party IDL libraries can be found at https://idlastro.gsfc.nasa.gov/other_url.html. Among them, we recommend the IDL Astronomy Users library (https://idlastro.gsfc.nasa.gov) maintained by Wayne Landsman and which is extensively used in HEALPix-IDL, David Fanning's IDL Coyote library (http://www.idlcoyote.com) from which some routines are used in HEALPix-IDL, and Craig Markwardt's IDL library (https://cow.physics.wisc.edu/~craigm/idl/idl.html).

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... version²

the command sw_vers -productVersion can be used to know the Mac OS X version being used

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...³

the command ls -lrt $HOME/Library/Preferences/*[xX]11*plist can be used to determine the X implementation and its configuration file

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