Natural Logarithm
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 This page describes the monadic arithmetic function. For the dyadic logarithm function, see Logarithm.
⍟

Natural Logarithm (⍟
), or Natural Log, is a monadic scalar function which computes the natural logarithm of the argument. Logarithm shares the glyph ⍟
with the dyadic arithmetic function Logarithm. The glyph, a composition of the glyphs for Circular (○
) and Exponential (*
) to indicate its close mathematical ties with these two functions, is a stylised tree log.^{[1]}
Examples
⍟1 2 (*1) (*10) 0 0.6931471806 1 10
Properties
Natural logarithm is a special case of Logarithm with the default left argument of e (*1
).
((*1)∘⍟ ≡ ⍟) 1 ¯1 0J1 1
Works in: Dyalog APL
Natural logarithm and exponential *
are inverses of each other, except where the natural log is undefined.
(⊢ ≡ ⍟∘*) 0 1 ¯1 0J1 1 (⊢ ≡ *∘⍟) 1 ¯1 0J1 ⍝ natural log of zero is undefined 1
Works in: Dyalog APL
External links
Documentation
References
 ↑ McDonnell, E. E.. Recreational APL: The Story of
○
. APL QuoteQuad, Volume 8, Number 2, 197712.