Redimensioning formal parameter arrays in OpenVMS BASIC, Revisited
I was working on a program on a VAX today, and needed to redimension dynamically allocated arrays that are passed to an external function. I've done this in the past (an old USENET post, and the old blog post that mentions it), but this time I managed to simplify my solution, and generalize it to work with both lower and upper bounds, and so the same function would work with multiple VMS BASIC data types. Here's the new USENET post. (How's that for thread necromancy?)
I'll include the code in this blog post, too, for ease of reference. Here's vax_redim_best.bas:
program vax_redim_best option type = explicit, constant type = integer, & size = integer long, size = real double record rec string s = 13 long i end record rec ! Don't declare the parameters, and everything works, even passing ! different types. external sub redim declare long stat, i i = 1 dim rec rec(1 to i) print "lbound (rec) at start: "; lbound (rec) print "ubound (rec) at start: "; ubound (rec) call redim (rec(), 3, 10) print "lbound (rec) after redim: "; lbound (rec) print "ubound (rec) after redim: "; ubound (rec) dim string s(1 to i) print "lbound (s) at start: "; lbound (s) print "ubound (s) at start: "; ubound (s) call redim (s(), 3, 10) print "lbound (s) after redim: "; lbound (s) print "ubound (s) after redim: "; ubound (s) dim long l(1 to i) print "lbound (l) at start: "; lbound (l) print "ubound (l) at start: "; ubound (l) call redim (l(), 3, 10) print "lbound (l) after redim: "; lbound (l) print "ubound (l) after redim: "; ubound (l) end program ! vax_redim_best function long redim (long s, long low, long high) option type = explicit, constant type = integer, & size = integer long, size = real double external long function bas$rt_dim_bounds (long by value, long by value, long by value) declare long r r = bas$rt_dim_bounds (loc (s), low, high) end function r ! redim
I'll just point out, which I failed to do in the old USENET post or
the new USENET post, that you have to use a variable when using
the VMS BASIC dim statement or you get a fatal runtime error. Ooops.
So use:
declare long i i = 5 dim string s(1 to i) ! Notice that last thing is the variable, i redim (s, 3, 10)
If you had said:
You'd have gotten the following error:
%BAS-F-PROLOSSOR, Internal error in VAX BASIC Run-Time Library. Please submit an SPR -BAS-I-FROFUN, In external function ALT_REDIM -BAS-I-FROMOD, In module Y %TRACE-F-TRACEBACK, symbolic stack dump follows module name routine name line rel PC abs PC 0004B2AA 0004B2AA ----- above condition handler called with exception 001A833C: %BAS-F-PROLOSSOR, Internal error in VAX BASIC Run-Time Library. Please submit an SPR -BAS-I-FROFUN, In external function ALT_REDIM ----- end of exception message 0004B2AA 0004B2AA ----- above condition handler called with exception 001A833C: %BAS-F-PROLOSSOR, Internal error in VAX BASIC Run-Time Library. Please submit an SPR ----- end of exception message 0004A352 0004A352 00054E37 00054E37 ALT_REDIM ALT_REDIM 43 0000002E 00000AC2 Y Y 24 0000015D 0000095D
Don't actually submit an SPR, of course: you did it to yourself by using an undocumented VMS BASIC internal runtime function.
Oh, I don't have access to an Alpha these days, so I haven't tried it
there, but I imagine using something named DBASIC$RT_DIM_BOUNDS
instead of DBASIC$RT_DIM would likely work there.
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