Returns the natural logarithm (base e) of the given argument
Implemented by: dartmouth2, dartmouth4, ansimin, hptsb, decbasic, altair8K, Applesoft, TI994, CBM, Atari, msatari, level2, colormc, BBC, GWBASIC, MSX, bwbasic, bw32, ABasiC, QBasic, VBDOS, FreeBASIC, Gambas
With variations:
Also written as: