[Jprogramming] dyad ": rounding error

[Dan Bron]

Roger wrote:

> The difference is that the dyad ": depends on the
> C library routines whereas 8!:x do the programming
> themselves

Is  8!:x  fast?  If so, is it feasible and desirable to implment  m ": n  for numeric  n  by calling   8!:x   under the covers?  Something along these lines:

	fmt =: verb define"1 _
		": y
	:
		'a b'=. <"_1 |: fmt&.> +. x
		
		k    =.  , L: 0
	
		;:^:_1 ('b< >' k (>a) k '.' k (>b)) 8!:0 y
	)

I'm sure that's buggy and incomplete, but it gives the gist.  

I will note that the  ;:^:_1  part annoys me, and this isn't the first time.  I wish I had a version of  8!:2  that put spaces between the formatted numbers.  For example, as opposed to:

	   '0.3' (8!:2) 9 9
	9.0009.000

I would like:

	   '0.3' (8!:3) 9 9
	9.000 9.000

Actually, in the above case,  ;:^:_1  probably isn't sufficient, due to layout and alignment, as in:
 
    	   1000001 _14 ((<1;1;0),(<0;0;2)) } i.  3 3 3
	      0  1 _14
	      3  4   5
	      6  7   8
	
	      9 10  11
	1000001 13  14
	     15 16  17
	
	     18 19  20
	     21 22  23
	     24 25  26

so maybe in the re-implementation of dyad  ":  only the individual scalar numbers should be formatted with  8!:0  .  The the spacing and layout should be left to the current algorithm.

-Dan