Re: Alternatives to MOVEL - just curious

On Mon, Dec 9, 2013 at 1:44 PM, Dave Shaw <daveshaw@xxxxxxxxxxxxx> wrote:

num4 = %dec(%subst(%char(num6):1:4):4:0);

I'm not sure it's more readable at a glance, but if you read through
it, I think [it documents the intention].

Fully agree here. Well, I'd say it's definitely NOT more readable at
a glance. ;) But it does document the intention.

I'm not sure how it'll perform, but it can't be worse than division.

It absolutely can be worse than division. Division is one arithmetic
operation. Yes, it's the most expensive of the four basic arithmetic
operations, but modern hardware usually is pretty quick at arithmetic.
%CHAR by itself is already potentially more expensive than a
division. You have to convert a number to a variable-length string,
and you have to put the decimal in the right place, if there is one.
Then you have to convert in the other direction with %DEC.

There's a lot of logic in generic conversion between numbers and
strings. (Some specialized conversions are faster than others. Zoned
format lends itself to quicker conversion on the i. MOVE-type
"conversions" are comparatively fast, because they have minimal logic
to them.) Arithmetic is almost no logic - usually just a single
hardware instruction.

John