Hello - I have studied the related language K in the past:
http://en.wikipedia.org/wiki/K_(programming_language) <http://en.wikipedia.org/wiki/K_(programming_language)>and just the other day I was very excited to discover J, which seems to have a better license and better GUI than K - so I am thinking of switching from K to J. I hope this is the right place to ask a "newbie" question - about whether J has "dependencies" and "triggers" like K. One feature from K which I really liked was dependencies and triggers, which are described as follows in an older K manual (KRefLite.PDF) available on-line: http://patch-tag.com/r/olegfink/icfpc/snapshot/current/content/pretty/kreflite.pdf <http://patch-tag.com/r/olegfink/icfpc/snapshot/current/content/pretty/kreflite.pdf> *A dependency is a global variable with an associated expression describing its relationship with other global variables. The expression is automatically evaluated whenever the variable is referenced and any of the global variables in the expression have changed value since the last time the variable was referenced.* (p. 35) *A trigger is an expression associated with a global variable that is executed immediately whenever the value of the variable is set or modified. The purpose of a trigger is to have side effects, such as setting the value of another global variable.* (p. 45) A short example using triggers and dependencies to implement database "drill-down" for OLAP (on-line analytical processing) can be found at the "No-Stinkin' Loops" website here: http://nsl.com/papers/drilldown.htm In the above example, a quoted string following a variable's attribute: ..d denotes a *dependency* which will be automatically evaluated any time the variable having this attribute is referenced (if any variables mentioned in the dependency have been changed) and a quoted string following a variable's attribute: ..t denotes a *trigger *which will be automatically evaluated any time the variable having this attribute is updated. As a learning exercise, I would like to port the drill-down example above from K to J. So I am curious whether J has mechanisms similar to K's dependencies and triggers. Alternatively, (if J lacks such mechanisms) I would be very appreciative for any ideas on how to go about simulating K's dependencies and triggers in J. Thank you. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
