APL Wiki Tutorial

The APL Wiki Tutorial contains several references to NARS2000 regarding extraordinary behaviour and/or missing features. See http://aplwiki.com/LearnApl/LearningApl

The following shall be a complete list of those issues. Used to make changes to the wiki when appropriate.

Chapter 6: "Writing a Function"

"Saving a workspace"

Using Windows default folder (NARS2000) versus current directory (other implementations).

Chapter 10: "Built-in Functions"

"Comparative Functions"

"Find" is not available

Chapter 14: "Error Handling"

Error Trapping, Debugging and Tracing

Currently NARS2000 offers both ⎕ELX Error Latent Expression and ⎕EA Execute Alternate for error trapping, two very helpful exception-handling / run-time-error-avoidance techniques or APL features, when used correctly.

To intentionally cause APL to halt just after the user-function line of code you wish to examine, place a line of APL code which looks something like 'a'÷1 right after the complex or not fully-understood line of code you wish to examine more closely. Since the APL interpreter cannot divide a string by a number, it will fail so you can examine the intermediary user-function results closely. Obviously, after you better understand how the user-function is working, you can then delete the 'a'÷1 intentionally inserted error, sometimes called code scaffolding since it is removed once the user function is corrected or complete - a process called debugging and or code testing. APL frequently makes use of complex idioms and debugging helps better understand the way the idiom(s) may be working. Important: Frequently comment your code with ⍝ so you remember what the code was supposed to be performing!

See also Examples/Files for a user-function example of ⎕ELX use. Default value for Quad ELX: ⎕ELX←"⎕DM"