Prev: Solving equations with ln()
Next: Simple? SysRPL question
From: John H Meyers on 9 Apr 2008 03:44
On Tue, 08 Apr 2008 23:44:32 -0500:

[use a library, if installed, assuming UserRPL]

Since a library may be stored in any port,
perhaps :&:nnn VTYPE should be tested
(this seems to error on HP49/50 "iff" library nnn is not found,
though I don't know whether this is guaranteed foolproof,
including against a library just stored but not yet installed);
it also doesn't error on HP48G[X], on which you just get -1 result,
and it's also theoretically possible to create a variable named 'nnn'
(anything "nnn" S~N STO)

One could also just plunge ahead and execute the first needed
library function, by number, e.g. #LLLNNNh LIBEVAL
(error #4 indicating that the function wasn't found).

Or dynamically compile a "visible" command name
e.g. "::WXYZ" STR\-> DTAG
and test for resulting object type; this is slower, however,
and also compiles a ROMPTR (type 14) only if library is also attached,
which not all libs need be (nor do all have any "visible" commands, etc.)

Note that whenever IFERR is used, flag -55 decides whether
last-saved user command arguments are restored after an error,
so one may need either to set or test the flag state,
to guarantee absence of a flag-dependency bug
(even HP has published programs neglecting that,
including APLY in the 48G AUR, also embedded in the HP48G[X] via TEACH)

[r->] [OFF]
 | 
Pages: 1
Prev: Solving equations with ln()
Next: Simple? SysRPL question