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From: pgcomp@pbinfo.UUCP (Projektgr. Uebersetzerbau)
Newsgroups: comp.lang.pascal
Subject: Re: C Ternary Conditional Expression?
Summary: RE: C Ternary Conditional Expression
Message-ID: <534@corona.pb>
Date: 26 May 89 09:41:15 GMT
References: <950025@hpclcdb.HP.COM>
Organization: Uni-GH Paderborn, Germany
Lines: 39


In article <950025@hpclcdb.HP.COM> cdb@hpclcdb (Carl Burch) writes:

>Can anyone think of a way to express in Pascal a form equivalent to the
>ternary conditional expression in C without using a separate statement?
>I need to speed up an expression that usually matches a cached value, but 
>can't figure out how to move the code out of the called function
>( represented by f(indx) below) to save the procedure call overhead.
>
>For instance, how could one translate :
>
> a[ (indx == last_indx) ? last_val : f(indx) ] = a [ y ];
>
>without using an IF statement?  Preferably without using a temporary variable.
>
>The only Pascal equivalent I've generated is :
>
> IF (indx = last_indx)
>    THEN temp := last_val
>    ELSE temp := f(indx);
> a[temp] := a[y];
>
>Please omit all flames - I just happen to know how to do this in C and nobody
>I've asked has been able to design a Pascal equivalent.
>


 Since BOOLEAN Values should be implemented as
   TYPE BOOLEAN = (FALSE,TRUE);
 
 simply try
   a[ord(indx=last_indx)*last_val+ord(indx<>last_indx)*f(indx)] := a[y];
 
 or 
   a[ord(indx=last_indx)*last_val+(1-ord(indx=last_indx))*f(indx)] := a[y];
   
 whichever is faster.

			 thomas roemke