Path: utzoo!attcan!uunet!cs.utexas.edu!samsung!munnari.oz.au!diemen!sol!quan
From: quan@sol.surv.utas.oz (Stephen Quan)
Newsgroups: comp.lang.c
Subject: Re: **** a simple question ****
Message-ID: <quan.653559525@sol>
Date: 17 Sep 90 08:18:45 GMT
References: <793@babcock.cerc.wvu.wvnet.edu>
Sender: news@diemen.utas.edu.au
Lines: 38

siping@cathedral.cerc.wvu.wvnet.edu (Siping Liu) writes:

>How can I print out ONLY the significant digits of
>a float number? As you know, "%f" fills in zero's if
>the number does not have enough non-zero digits after
>the point.
>
>I'd like to have:
>  for 3.12, print out 3.12;
>  for 3.0, print out 3.0;
>  for 3.12349, print out 3.1235;  (4 digits at most after the point)

>siping@cerc.wvu.wvnet.edu

Well let's see now, try this, maybe not efficient but short!

printreal(num)
float num;
{
  char tmp[20];
  int i;
 
  /* get the number in nearly the format required.  It even rounds up! */
  sprintf(tmp,"%1.4f",num);
  
  /* eliminate trailing zeros. */
  /* for loop 1 just finds the end of the list. */
  /* for loop 2 works backwards from end, eliminating the zeros. */
  for (i=0 ; tmp[i] ; i++);
  for (i-- ; (i>0) && (tmp[i]=='0') && (tmp[i-1]!='.') ; i--) tmp[i] = '\0';
  
  /* print the formatted number out. */
  printf("%s",tmp);
}

Stephen Quan, (quan@sol.surv.utas.edu.au)
University of Tasmania,
Aussie.