Re: bc and dc. (Was: neatroff for Russian.)

[Alejandro Colomar]

Hi Ralph,

On 4/28/23 11:34, Ralph Corderoy wrote:
> Hi Alejandro,
> 
> None of the below may apply to GNU's bc and dc.  I prefer Unix.
> 
>> bc(1) on the contrary, is likely to be using 'long double', for being
>> able to provide so many digits.
> 
> No, bc doesn't use a C language or machine type.  The precision can
> be set.
> 
>     $ bc -l
>     scale=42
>     l(1114112) / l(2)
>     20.087462841250339408254066010810404354011270
>     $
> 
> bc's l() function is written in bc rather than a built-in and can be
> read for fun.  bc uses dc(1) to do the work and can be asked to ‘compile
> only’ with -c.  dc has k to set the precision; bc's scale simply uses k.

Would you please share that?  I'm curious.  I could only see this:


$ echo 'l(1114112) / l(2)' | bc -lc
@iK1114112:C2,0:K2:C2,0:/W@r
@i


$ echo 'l(1114112) / l(2)' | /usr/lib/plan9/bin/bc -c
 1114112 l<12>x 2 l<12>x/ps.
q


$ echo 'l(1114112) / l(2)' | /usr/lib/plan9/bin/bc -lc
c[cannot open input file:1, ]pc
 1114112 l<12>x 2 l<12>x/ps.
q

> 
> dc uses a byte to store each pair of decimal digits.  This allows
> overflow within the byte during calculations and makes it quick to
> perform the common case of formatting the many-byte number to
> decimal-digit text.

Makes sense.

Cheers!
Alex

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