OPM does IMPORT/EXPORT, too

[Gene Gaunt <issgg@xxxxxxx>]

Use RSLVDP (Resolve Data Pointer) when you don't know a variable name until 
runtime.  The target variable must have attributes STAT EXT.  The RSLVDP 
third operand is a progam pointer denoting which activation to search in 
the current activation group.  A null third operand means search all 
activations in the current activation group in reverse order.  The second 
operand is the variable name.  The first operand receives a data pointer. 
 A recursion level qualifier isn't needed here because EXT variables are 
static and thus shared by recursion.  The RSLVDP instruction and the target 
EXT variable may be in different programs!  This lays the foundation for an 
IMPORT/EXPORT feature in an OPM compiler.  Here's an example.

dcl dd     January     stat char(11) ext;
dcl dd     February    stat pkd(5,2) ext;

dcl dtaptr Chameleon   auto;
dcl dd     VarName32   auto char(32);

cpyblap    VarName32, "JANUARY", " ";    -- prepare variable name
rslvdp     Chameleon, VarName32, *;      -- point to January
cpybla     Chameleon, "hello there";     -- modify January (character)
cpyblap    VarName32, "FEBRUARY", " ";   -- prepare variable name
rslvdp     Chameleon, VarName32, *;      -- point to February
cpynv      Chameleon, P"123.45";         -- modify February (packed) 

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