AS=PFSDIP(RL,A)
$(POLYNOMIAL FROM SPECIAL DISTRIBUTIVE POLYNOMIAL. A IS A DISTRIBUTIVE
POLYNOMIAL IN RL VARIABLES, RL NON-NEGATIVE. AS IS THE RESULT OF
CONVERTING A TO A RECURSIVE POLYNOMIAL IN RL VARIABLES.)
SAFE AL1,EL1,E1.
(1) $(A=0.) IF A=0 THEN ( AS=0. RETURN ).
(2) $(RL=0.) IF RL=0 THEN ( AS=FIRST(A). RETURN ).
(3) $(RECURSION.) AS=(). AP=A. RLP=RL-1. REPEAT
( EL=SDIPDG(RL,AP). A1=(). REPEAT ( EL1=SDIPDG(RL,AP).
IF EL1=EL THEN ( ADV2(AP.AL1,E1,AP). IF EL1 GT 0 THEN E1=RED2(E1).
A1=COMP2(E1,AL1,A1) ) ) UNTIL EL1 LT EL OR AP=(). A1=INV(A1).
AS1=PFSDIP(RLP,A1). AS=COMP2(AS1,EL,AS) ) UNTIL AP=().
AS=INV(AS). RETURN..