Migration level

, Evolution level, or Compatibility setting is a number that, in Dyalog APL, APL+Win, and APLX respectively, specifies exact behaviour relative to APL2. In Dyalog APL and APL+Win, a lower value represents a behaviour closer to the original NARS specification, while a higher the value represents a behaviour closer to APL2. In APLX, a lower value matches APL2 while a higher value indicates higher backwards compatibility with APL.68000.

APL+Win settings
APL+Win's default is.

Work-arounds
APL+Win provides system function alternatives to the functions that are affected by moving to evolution level 2:

Dyalog settings
Dyalog's default setting is currently.

Work-arounds
When migrating to Dyalog APL, the below drop-ins for the affected built-ins allow setting  while preserving code behaviour. It is then safe to programmatically (as shown in the rightmost column) change all occurrences of the affected built-ins with their respective covers.

Alternatively, the definitions can be used directly inside the text substitutions, whereby one avoids polluting existing code with these cover names.

APLX settings
APLX treats the value as a collection of individual bits, thus allowing the combination of an exact set of behaviours:

Documentation

 * Dyalog
 * APLX