Why in lisp (Emacs Lisp and Scheme as I know) construction like (*) returns 1?
What I multiply here? How can I call this function * without arguments?
Why in lisp (Emacs Lisp and Scheme as I know) construction like (*) returns
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Why in lisp (Emacs Lisp and Scheme as I know) construction like (*) returns 1?
What I multiply here? How can I call this function * without arguments?
This is a mathematical convention: the product of an empty sequence of numbers is one, by definition; note that one is the identity element for multiplication (1×a = a×1 = a). This is convenient because you can call
*with a variable number of arguments without worrying about the case where there are no arguments present.Similarly, the sum of an empty sequence of numbers is zero, the identity element for addition. Try issuing
(+)at your Lisp prompt.