an introduction to MI by example II part B

Well if this is a small-size race (just for fun), here's my entry to get the 
caller's library name.

dcl spcptr ?Library    parm;
dcl dd     Library     bas(?Library) char(10);
dcl ol     MainList    (?Library) parm ext min(1);
dcl spcptr ?Mat        auto init(Mat);
dcl dd     Mat         auto char(12816) bdry(16);
dcl dd     MatSize     def(Mat) pos(1) bin(4) init(12816);
dcl dd     Level       def(Mat) pos(9) bin(4);
dcl dd     Item(2:101) def(Mat) pos(17) char(128);
dcl sysptr ?Pgm(2:101) def(Item) pos(33) aeo(128);

-- return library name of caller

entry     Main (MainList) ext;   -- start here
matinvs   ?Mat, *;               -- get call stack
matptr    ?Mat, ?Pgm(Level);     -- get pointer info
cybla     Library, Mat(12:10);   -- extract library
pend;                            -- implicit RTX

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