APEX introduced Array Morphology as a generalization of data flow analysis for array languages.
Robert Bernecky's MSc thesis describes the compiler and details its
performance. The APEX thesis is available here: PDF (651 KB).
A related Technical Report describes the internals of the APEX compiler in more detail. The Technical Report is available here: PDF (133 KB).
Other downloadable papers on compiled APL include:
Reducing Computational Complexity with Array Predicates
ACORN: APL to C on Real Numbers
The APEX compiler is available under the GNU Public License, version 2 for operation under Linux and other civilized operating systems. BillWare(tm) need not apply. APEX requires a Dyalog APL interpreter (available for free to students, and at reasonable prices to those who have ceased learning, at //http://www.dyalog.com), as well as the SAC compiler that compiles APEX-generated code. SAC may be obtained at http://www.sac-home.org, but licensing details for SAC remain up in the air as of 2007-10-17.
APEX Version 0.0.0 is now available for download. That file comprises Dyalog APL workspaces, Jim Weigang's source-level interchange versions of those workspaces, related text files, and over 130 APL benchmarks and unit tests. The tar file is here: