Lambert W Function (hp-42s)

[Bill Triplett]

This work is beautiful.

In case a user does not care so much about minimum program space, here is a version based on Albert Chan's post from 10-06-2020, 01:20 AM. This version outputs W(x) instead of e^W(x), and empties the stack:

Code:

00 { 64-Byte Prgm }
01▸LBL "cW"
02 0.3
03 -1
04 E^X
05 RCL+ ST Z
06 STO× ST Y
07 STO+ ST X
08 LASTX
09 STO+ ST Z
10 ×
11 SQRT
12 +
13 X<>Y
14 +/-
15 X<>Y
16▸LBL 01
17 X=Y?
18 GTO 02
19 STO ST Y
20 LN
21 1
22 +
23 R^
24 RCL+ ST Z
25 X<>Y
26 ÷
27 -
28 STO× ST X
29 LASTX
30 STO+ ST Y
31 GTO 01
32 LBL 02
33 LN
34 X<>Y
35 CLX
36 STO ST Z
37 STO ST T
38 X<>Y
39 RTN
40 END