There are optimizations but they require that you 
express the computation differently, in this case as
+/@:< .  The optimizations are listed in Appendix B
of the dictionary.
http://www.jsoftware.com/help/dictionary/special.htm

You can detect that special code is being employed
by doing some benchmarks.  e.g.

   x=: 5
   y=: 1e6 [EMAIL PROTECTED] 10

   ts=: 6!:2 , 7!:[EMAIL PROTECTED]  NB. time and space

   ts '+/x<y'
0.00817115 1.0496e6
   ts 'x +/@:< y'
0.00583091 1152



----- Original Message -----
From: Terrence Brannon <[EMAIL PROTECTED]>
Date: Wednesday, March 28, 2007 12:57 pm
Subject: [Jgeneral] optimization of array passes?

> Given this verb:
> 
>   +/ 4 < 3 1 4 1 5 9
> 
> does it go through the list once with the verb < and then again 
> with the verb +/
> or can it do it in one pass like I could in C?
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