Re:Array Languages: R vs. APL
by bruturis on Friday March 22, 2024 @05:34AM
(#39788869)
You are right, the correct code is .</ +. >./
To understand this you need to know that >. and <. are the min and max functions, and that in J three functions separated by spaces, f g h, constitutes a new function mathematically defined by (f g h)(x) = g(f(x), h(x)). An example is (+/ % #) which applied to a list gives the mean of the list. Here +/ gives the total, # gives the number of elements and % is the quotient.
To understand this you need to know that >. and <. are the min and max functions, and that in J three functions separated by spaces, f g h, constitutes a new function mathematically defined by (f g h)(x) = g(f(x), h(x)). An example is (+/ % #) which applied to a list gives the mean of the list. Here +/ gives the total, # gives the number of elements and % is the quotient.