(12C) log1p function

[Albert Chan]

Hi, Dieter

Typo fixed. Thanks.

A (quite) accurate ln1+x function, or "how close can you get" part II thread had the same formula.
Was there a part I ?

My rpn.exe confirmed +correction way much better, and avoided divide-by-0 test.

Quote:>rpn
1.23456789e-3 s
1+ log s1 ? # log1p value
0.001233806437707756434884160067124232513609
r 1+ =-10 s2 ? log s3 ? # 1+X, LN(1+X) value
1.001234568
0.001233806547572121411586143127131058379588

- ?10 # correction wanted
-1.09864365E-10

r2 1- r $ - r2 / ?10 # correction = -(X+1-1-X)/(X+1)
-1.09864365E-10

r3 r x r2 1- / r3 - ?10 # correction = log1p(X) * X / (1+X-1) - log1p(X)
-1.099321546E-10