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Issues when converting

From APL+Win to Dyalog APL

Primitives and syntax

  • For (a a)←1 2 APL+Win sets a←1 but Dyalog sets a←2. This is hard to fix, but probably a rare occurrence.

  • If both arguments are empty , and ⍪ return their left argument in Dyalog but their right argument in APL+Win

  • "-delimited character constants can be automatically transformed to use ' quotes but ⍎ will fail on a '-delimited expression that contains "-delimited text.

  • Pass-though value of modified assignment is the expression on the left in APL+Win but the expression on the right in Dyalog.

System constants

  • ∆SYSVER looks at the executable timestamp, but the interpreter does actually know when it was created, as shown in the About box

  • ⎕SINL cannot be modelled, but is unlikely to appear in code; use )SINL.

System variables

  • ⎕RL not fully modelled (missing two RNGs and ∆RL is not updated when generating); only ⎕RL← should be replaced with ∆RL←.

  • ⎕PR is impossible to model. R is a character singleton or empty vector. If R is empty, ⍞ input is returned with the prompt included in the result, including any changes user has made. If R is a character, that character replaces each unmodified element of the prompt in the result. ⎕PR has no effect when ⎕ARBOUT ⍳0 is used.

  • ⎕WATCHPOINTS would be very nice to have

System functions

  • Dyadic ⎕DR is complex and does multiple advanced things, including data (de-)serialisation using binary or XML form.

  • ⎕CALL and ⎕STPTR cannot be modelled, but is usually easy to rewrite to pure APL.

  • Skipping ⎕DEFL for now as not worth the effort, though totally doable.

  • ⎕IDLOC is hard (WIP)

  • User commands are different, so ∆UCMD is unlikely to work as ⎕UCMD

  • ∆INBUF isn't perfect, but it does allow basic things.

  • ∆CRLPC cannot read public comments from locked functions

  • ⎕LOG is part of the larger logging system. It writes timestamped and optionally (left arg) event-typed entries a log file.

  • ⎕CFINFO and ⎕DTR are not implemented

Keywords

  • :Assert expr is a comment at runtime, but an assertion when running in debug mode

  • :Debug expr is a comment at runtime, but an :if DEBUGMODE ⋄ {}… if in debug mode

  • :Trace… is part of the larger logging system. It is skipped unless in test mode. It is equivalent to :IfTest ⋄ ⎕LOG…

Control structures

Conditionals

  • :And and :Or are short-circuiting ∧ and ∨ like :AndIf and :OrIf but for inline expressions, and :Ex allows intermediary execution (like statements between :If and :AndIf/:OrIf)

  • :IfTest is :If TESTMODE

Error Trapping

  • :Try is :Trap 0

  • :TryAll is similar to the effect of setting ⎕ELX„'…⎕LC+1' but without the problems doing so could cause in called functions.

  • Rather than :Case by error number, APL+Win has :CatchIf val≡⎕DM↑⍨¯1+⎕DM⍳⎕TCNL which can be abbreviated to :Catch val — I suggest we allow :Trap 'DOMAIN ERROR'and :Case 'DOMAIN ERROR' etc.

  • :Test block is part of the larger logging system. It is skipped unless in debug mode. The :Pass block requires all statements to work without error, while the :Fail block requires all statements to error.

Select

  • :NextCase is the opposite of break in C-like languages, i.e. where C continues the the next case, APL jumps to :EndSelect at the end of a :Case block, but :NextCase allows continuation. The current substitution to →2+⎕LC fails if there are diamonds instead of line breaks.

  • :Like is like :Case except it takes a globbing pattern and matches the selected-for value against this. IMO such :Select statements should be written as :If/:ElseIf with an expression to do the matching.