Re: why do ceil/floor give the decimal dot?

[Vincent Lefevre <vincent@vinc17.net>]

On 2015-05-14 10:54:26 -0700, Bart Schaefer wrote:
> No, I mean that looking at this:
> 
> torch% float X=27
> torch% print $X
> 2.700000000e+01
> torch% print $(( X ))
> 27.
> torch% printf "%f\n" $X        
> 27.000000
> torch% printf "%g\n" $X
> 27
> 
> One might wonder why there are four different representations of the
> same number, and we could therefore discuss whether some of them should
> be unified.  This is not the same discussion as whether they should be
> converted to integers.

Concerning the accuracy:

ypig% float x=$((1./3))
ypig% print $x
3.333333333e-01
ypig% print $((x))
0.33333333333333331
ypig% printf "%f\n" $x
0.333333
ypig% printf "%g\n" $x
0.333333

The last two are specified by C, and I suppose that $((x)) gives full
accuracy, i.e. if the decimal number is re-read as a floating-point
value, the original value must be recovered exactly.

Concerning the first one, I wonder why there are "typeset -E" (default
for "float" as used above) and "typeset -F". The way a value is output
shouldn't come from its declaration. IMHO, there should be a single
floating-point datatype, not one for each output format.

BTW, there is a bug in zsh 5.0.7:

ypig% typeset -F 3 x=$((17))
ypig% print $x
17.000
ypig% typeset -F 2 x=$((17))
ypig% print $x              
17.00
ypig% typeset -F 1 x=$((17))
typeset: invalid base (must be 2 to 36 inclusive): 1

It is not a base here.

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)