HP49-50G Lambert function

[Gil]

As some characters were missing in the previous transcription, here is a new format of the exact identical code:

Always version 2

\<< "
Lambert W(Z)
:
Having result Y

Y real
 in (
-879.3 
\oo)
or 
Z complex (a,b)

W(Z) finds / gives X
such that
(X * EXP X) = Z
W(X * EXP X) =X

" DROP \-> Y
\<<
IF Y TYPE 1. == NOT
THEN
IF Y -1. EXP NEG <
THEN Y 0. R\->C 'Y' STO
END
END
IFERR 'X' 'X' RCL
THEN
ELSE
END
IF Y TYPE 1. ==
THEN DUP2 SAME NOT
IF
THEN 'X' PURGE
END 'a*EXP(a)*COS(b)-b*EXP(a)*SIN(b)' Y OBJ\-> DROP = 'a*EXP(a)*SIN(b)+b*EXP(a)*COS(b)' Y C\->R SWAP DROP = 2. \->ARRY 'a' 'b' 2. \->ARRY [ 1. 1. ] MSLV OBJ\-> DROP R\->C UNROT DROP2
ELSE 'X*EXP(X)-Y' 'X' 1. ROOT
END UNROT DUP2 SAME
IF
THEN DROP2 'X' PURGE
ELSE SWAP STO
END "W(" Y + ")" + \->TAG
\>>
\>>

Regards,
Gil Campart