Date:         Fri, 26 Oct 2001 20:21:13 +0100
Reply-To:     John Whittington <John.W@MEDISCIENCE.CO.UK>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         John Whittington <John.W@MEDISCIENCE.CO.UK>
Subject:      Re: Character to numeric conversion
Comments: To: Dale McLerran <dmclerra@MY-DEJA.COM>
In-Reply-To:  <E15xA5k-000117-00@relay1.netnames.net>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 09:40 26/10/01 -0700, Dale McLerran wrote:

>.... I would recommend that you not employ implicit type conversion using
>the multiply by 1 approach which you mention.  That is an inefficient
>approach.  It is better to use explicit type conversion.

Dale, I think we've been through this one before! - it really depends upon
what one means by 'inefficient'.  I think we can probably all agree that
implicit conversion is not very good programming practice, not the least
because it undermines the value of 'implicit conversion messages' in the
log as a useful means of flagging programming errors - and therefore many
result is wastage of user time ('inefficient').  However, if you are
talking about efficiency in terms of run-time execution speed, then, if
anything, implicit conversion seems to slightly 'win' (following log from
SAS 8.2 on steam-powered Win95 PC):

670  data _null_ ;
671     c = '6' ;
672     start = time() ;
673     do i = 1 to 1e7 ;
674        n = c * 1 ;
675     end ;
676     elapse = time() - start ;
677     put 'time taken = ' elapse 5.2 ' seconds' ;
678  run ;

NOTE: Character values have been converted to numeric values at the places
given by:
       (Line):(Column).
       674:11
time taken = 13.57 seconds
NOTE: DATA statement used:
       real time           13.61 seconds

679  data _null_ ;
680     c = '6' ;
681     start = time() ;
682     do i = 1 to 1e7 ;
683           n = input(c, best32.) ;
684     end ;
685     elapse = time()-start ;
686     put 'time taken = ' elapse 5.2 ' seconds' ;
687  run ;

time taken = 14.00 seconds
NOTE: DATA statement used:
       real time           14.06 seconds

Kind Regards,


John

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