Hi David,
I believe that the IBM specified behavior is only achievable (if at all)
with platform specific (actually terminal specific) APL variants. The header
on page 335 says:
*⎕TC Contains a three-item character vector of terminal control characters:
⎕TC[1]—backspace
⎕TC[2]—new line (return)
⎕TC[3]—line feed*
This is what GNU APL has implemented, taking ASCII verbatim:
* ⎕UCS ⎕TC
8 13 10*
These numbers come from ASCII rather than from Unix. Then the purpose of
⎕TC is explained:
*Use ⎕TC rather than ⎕AV to avoid system dependencies (because the**
**order of ⎕AV is different in different APL implementations**).*
This assumes that the same character - take newline as an example - may
be located at different positions
of the ⎕AV but behaves identically otherwise. But then the display vs.
typewriter example shows that this is
not the case. I would add the Windows vs. Unix example where newline may
or may not imply a carriage
return.
If we would use *curses* as Elias suggested earlier that we could easily
violate the '*three-item character vector*'
spec in the header.
Taking this all together tells me that ⎕TC, which was mainly provided
for IBM code compatibility and not for real
use in new programs, is a stone-age left-over (I remember having it seen
in classical APL but never used) should
remain as is.
Thank you nevertheless for pointing this out!
/// Jürgen
On 05/31/2014 08:50 PM, David B. Lamkins wrote:
See IBM Reference, page 335.
⎕tc[2] and ⎕tc[3] differ from the IBM-specified behavior, presenting as
Unix format effectors rather than as APL format effectors.
In particular, APL specifies that ⎕tc[2] should advance the print
position to the start of the next line and ⎕tc[3] should advance the
print position downward one line while retaining the current column
position.
The current behavior of ⎕tc[1] is acceptable according to the IBM
Reference.
