Bo Jacoby wrote:
> I wonder how to translate this explicit verb into a tacit verb?
> E=. 4 : '(y+x*1&o.)^:_ y'
How about:
Et=: ,~ (p. 1&o.)^:_ ]
0.0167 (E-:E2) 0.46478
1
The key insight is that x f^:n y is x&f^:n y . That is, the
right-argument to dyadic power is "carried through" all the
iterations (and we need the initial values of both x and y carried through all
iterations, hence the , ). I guess a second,
minor insight is that y+x*u is just a polynomial evaluated at u , which
allows us to use p. to avoid picking apart this fixed
argument (and the coefficient vector for p. is always "reversed", hence the
~ on the , ).
-Dan
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
