Rounding Algorithms?

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1 total messages Started by Frank Hrebabetzky - CERTI - CCE ... Mon, 01 Apr 1996 02:45

#1244

Author: Frank Hrebabetzky - CERTI - CCE ...
Date: Mon, 01 Apr 1996 02:45

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Some time ago I wrote some procedures for rounding real numbers:

PROCEDURE round (x:LONGREAL; n:INTEGER): LONGREAL;
(* Round x to n digits. *)

PROCEDURE roundp (x:LONGREAL; n:INTEGER): LONGREAL;
(* Round x to n digits behind the decimal point. *)

PROCEDURE RealToStr (x:LONGREAL; n:INTEGER; VAR s:ARRAY OF CHAR);
(* Convert x to s, rounding to a total of n characters.
   n>0: floating point, else exponential.
*)

I am not so happy with my solutions, because I use logarithms and 
exponential functions to generate power-of-10-factors for left- and 
right-shifting and ENTIER for truncation. Sometimes arithmetic errors in 
those functions give me a result of 9.99 when I want to round 10. 

Does anybody know procedures or algorithms or references about that topic? 


Thanks in advance.

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Fundacao CERTI			Tel.:	+55 / 48 / 234-3000
Dr. Frank Hrebabetzky		Fax:	+55 / 48 / 234-1514
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88040-970
Brasil

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