[CLN-list] CLN-list Digest, Vol 91, Issue 2
Po-Hsun Tseng
zengbs at gmail.com
Tue Feb 11 01:35:19 CET 2020
Thanks, it works for me!
Po-Hsun Tseng (Rocky)
On Mon, Feb 10, 2020 at 7:00 PM <cln-list-request at ginac.de> wrote:
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> Today's Topics:
>
> 1. Re: adding two different precision number (Po-Hsun Tseng)
> 2. print multi-precision floating number in scientific notation
> (Po-Hsun Tseng)
> 3. Re: print multi-precision floating number in scientific
> notation (Richard B. Kreckel)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 9 Feb 2020 21:35:30 +0800
> From: Po-Hsun Tseng <zengbs at gmail.com>
> To: Bruno Haible <bruno at clisp.org>
> Cc: cln-list at ginac.de
> Subject: Re: [CLN-list] adding two different precision number
> Message-ID:
> <
> CA+HRcQvs_sxgtgZU7z4qR_1shrhTo2YWmNPfee2Lx9gDpdQkPg at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Dear Bruno,
>
> Thank you for your quick and detailed reply.
>
> Po-Hsun Tseng (Rocky)
>
>
> On Sun, Feb 9, 2020 at 6:37 PM Bruno Haible <bruno at clisp.org> wrote:
>
> > Hi,
> >
> > > 1. Does CLN support performing two different precision number with
> basic
> > > overloading operators (+,-,*, and /)?
> >
> > Yes.
> >
> > > 2. If yes, how does CLN treat that? eg. zero padding on the
> > precision-less
> > > number before doing operation?
> >
> > It does zero-padding on the operand with the smaller precision, then the
> > operation on the then equal-size operands, and finally rounding
> > (round-to-even)
> > to the smallest precision among the operands.
> >
> > Example (using decimal numbers for illustrative purposes):
> >
> > 3.14149265358979323
> > + 2.718282
> > ---------------------
> > 3.14149265358979323
> > + 2.71828200000000000
> > ---------------------
> > 5.85969465358979323
> > ---------------------
> > 5.859695
> >
> > Therefore, when some computation returns a result, usually a few decimal
> > places at the end can be wrong, but CLN will never give you a 50-digit
> > result when in fact the accurary is only 10 digits - UNLESS you use
> > conversion functions [1] explicitly.
> >
> > Bruno
> >
> > [1] https://www.ginac.de/CLN/cln.html#Conversion-functions
> >
> >
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> ------------------------------
>
> Message: 2
> Date: Mon, 10 Feb 2020 12:38:44 +0800
> From: Po-Hsun Tseng <zengbs at gmail.com>
> To: cln-list at ginac.de
> Subject: [CLN-list] print multi-precision floating number in
> scientific notation
> Message-ID:
> <CA+HRcQuDUsm_F54LNyHnJMaffYZuAFJQTWiCKVN_YXt=
> RgV3ig at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Hi CLN developers,
>
> Sorry for frequently asking questions. I have checked manual and searched
> mailing list for full example, but nothing inside. Moreover, I only
> familiar with C...
> Question: How to use `print_float()` to print multi-precision floating
> number in scientific notation on terminal? below is the full code I have
> ever tried, but it always gives me compilation error.
> thanks.
>
> #include <cln/io.h>
> #include <cln/float.h>
> #include <cln/float_io.h>
>
>
> using namespace cln;
>
> int main( ) {
>
> int N = 10;
>
> cl_F x[N];
>
> for (int i=0 ;i<N;i++) x[i] =
> "0.333333333333333333333333333333333333333333333333333333333333";
>
> // cl_print_flags.float_readably = true;
>
> for (int i=0 ;i<N;i++) print_float(stdout,
> cl_print_flags.float_readably, x[i]);
>
> return 0 ;
> }
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> ------------------------------
>
> Message: 3
> Date: Mon, 10 Feb 2020 10:23:06 +0100
> From: "Richard B. Kreckel" <kreckel at in.terlu.de>
> To: cln-list at ginac.de
> Subject: Re: [CLN-list] print multi-precision floating number in
> scientific notation
> Message-ID: <937a1dc6-ab90-c80c-932e-691b864a2f03 at in.terlu.de>
> Content-Type: text/plain; charset=utf-8
>
> Hi,
>
> You should first create the desired cl_print_flags object and then pass
> it as reference to the print_float function, like this:
> cl_print_flags flags;
> flags.float_readably = true;
> print_float(std::cout, flags, x[i]);
>
> Note also that stdout is not a C++ stream. I've replaced it with cout.
>
> -richy.
> --
> Richard B. Kreckel
> <https://in.terlu.de/~kreckel/>
>
> On 10.02.20 05:38, Po-Hsun Tseng wrote:
> > #include <cln/io.h>
> > #include <cln/float.h>
> > #include <cln/float_io.h>
> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
> > using namespace cln;
> > ?
> > int main( ) {
> >
> > ? ? int N = 10;
> > ?
> > ? ? cl_F x[N];
> > ?
> > ? ? for (int i=0 ;i<N;i++) x[i] =
> > "0.333333333333333333333333333333333333333333333333333333333333";
> > ? ?
> > // ? ?cl_print_flags.float_readably = true;
> > ?
> > ? ? for (int i=0 ;i<N;i++)?print_float(stdout,
> > cl_print_flags.float_readably, x[i]);
> > ??
> > ? ? return 0 ;
> > }
>
>
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>
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> End of CLN-list Digest, Vol 91, Issue 2
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