%%HP: T(3)A(R)F(.);
@ GAUSSELM by Robert Brunner
DIR
  QR
    \<< TRN CONJ DCMP
OVER DUP 2 \->LIST 0
CON { } \-> a n m r q
      \<< a 1 GET DUP
DUP ABS / DUP ROT
DOT 'r' { 1 1 } ROT
PUT 'q' SWAP STO+ 2
n
        FOR i a i
GET DUP \-> ai
          \<< 1 i 1 -
            FOR j
DUP q j GET DUP ai
DOT 'r' { j i } ROT
PUT DUP ROT DOT * -
            NEXT
DUP ABS / DUP ai
DOT 'r' { i i } ROT
PUT 'q' SWAP STO+
          \>>
        NEXT q RCMP
TRN CONJ r
      \>>
    \>>
  LU
    \<< DCMP OVER IDN
DUP 0 CON DCMP
DROP2 SWAP DCMP
DROP2 1 DUP DUP
RCLF \-> a m n l p pr
pc sr flg
      \<<
        WHILE pr m
< pc n \<= AND
        REPEAT 1 CF
          WHILE 1
FC? pc n \<= AND
          REPEAT pr
'sr' STO
            WHILE 1
FC? sr m \<= AND
            REPEAT
              IF a
sr GET pc GET
              THEN
1 SF
              ELSE
'sr' INCR DROP
              END
            END
            IF 1
FC?
            THEN
'pc' INCR DROP
            END
          END
          IF 1 FS?
          THEN
            IF pr
sr \=/
            THEN
'p' pr sr SWRW 'l'
pr sr SWRW 'a' pr
sr SWRW
            END a
pr GET DUP pc GET \->
pivr piv
            \<< pr 1
+ m
              FOR i
a i GET DUP pc GET
piv / DUP l i GET
pr ROT PUT 'l' i
ROT PUT pivr * -
'a' i ROT PUT
              NEXT
            \>>
          END 'pr'
INCR 'pc' INCR
DROP2
        END p RCMP
l RCMP m IDN + a
RCMP flg STOF
      \>>
    \>>
  DCMP
    \<< OBJ\-> OBJ\->
DROP DUP2 * OVER 1
- \-> m n mn n1
      \<< 1 m
        FOR i n
\->ARRY mn n1 i * -
ROLLD
        NEXT m
\->LIST m n
      \>>
    \>>
  RCMP
    \<< OBJ\-> OVER
SIZE OBJ\-> DROP OVER
\-> m n st
      \<< 1 m
        START OBJ\->
DROP 'st' n 1 -
STO+ st ROLL
        NEXT 1 n 1
-
        START st
ROLL
        NEXT { m n
} \->ARRY
      \>>
    \>>
  SWRW
    \<< \-> i j
      \<< DUP i GET
SWAP DUP DUP j GET
i SWAP PUT j ROT
PUT
      \>>
    \>>
END