Enhanced Debugging with Function Keys

Sometimes I want an additional functionality in the IDE. (Are you a RIDE user? We’ll cover that too!) For example, the other day, I was tracing through some very long functions to find an error which was being caught by a trap. Since the error was being caught, I couldn’t just let the function run until it would suspend. Again and again, I would press too many times, causing the error to happen and be trapped, and thus having to start all over again.

I wish I could select a line and run until there, I thought. Sure, I could set a break-point there and then continue execution, but that would drop me into the session upon hitting the break-point, and then I’d have to trace back into the function, and remember to clear the break-point. A repetitive work-flow indeed.

Make it so!

Luckily, I know someone who loves doing repetitive tasks: ⎕PFKEY. This is what I needed done:

  1. Toggle break-point (to set it)
  2. Resume execution
  3. Trace
  4. Toggle break point (to clear it)

A quick look in Options > Configure… > Keyboard Shortcuts > Code revealed that the command codes for these are BP, RM, TC, and BP again, so I tried:

      'BP' 'RM' 'TC' 'BP' ⎕PFKEY 10
 BP  RM  TC  BP 

I defined a simple function to test it with, and traced into that:

      ⎕FX 'f',⎕D
      ⎕VR 'f'
[1]   0
[2]   1
[3]   2
[4]   3
[5]   4
[6]   5
[7]   6
[8]   7
[9]   8
[10]  9

Tracing into f

Then I clicked on the line with a 7 on it, pressed , and lo:

Suspended on line 7

Keep it so!

Of course, I wouldn’t want to be bothered with setting this up in every session. So here’s a trick to set up F-keys (or anything else for that matter). When Dyalog APL starts up, it will look for MyUCMDs\setup.dyalog in your Documents folder ($HOME/MyUCMDs/setup.dyalog on non-Windows). If this file contains a function named Setup, it will be run whenever APL starts:

[1]  '<F10> is: ','BP' 'RM' 'TC' 'BP' ⎕PFKEY 10
[2]  ∇

And now, when I start APL:

New Session

Cool, but how about the RIDE?

Right, the RIDE doesn’t support ⎕PFKEY. However, Edit > Preferences > Shortcuts lets you both find the relevant command codes and assign them to F-keys. Just put <BP><RM><TC><BP> (type or paste those sixteen characters, with angle brackets and everything — don’t press the keys they symbolise!) in the PF10 input field:

Setting F10

The RIDE saves these preferences for you. Note that you can’t assign F-keys in $HOME/MyUCMDs/setup.dyalog because ⎕PFKEY has no effect in the RIDE, but you can still use that file to initialise other things.

Taking it one step further…

After using this for a while, I realised that I often want to “step into” a specific line . That is, I found myself pressing and then (the default keystroke for tracing). So I’ve assigned the same sequence, but with an additional trailing TC action:

[1]  '<F10> is: ','BP' 'RM' 'TC' 'BP' ⎕PFKEY 10
[2]  '<Ctrl>+<F10> is: ','BP' 'RM' 'TC' 'BP' 'TC' ⎕PFKEY 34
[3]  ∇

And for the RIDE, I set PF34 (which by default is invoked with ) to <BP><RM><TC><BP><TC>:

Setting Ctrl-F10