[erlang-questions] display floats without -e?

PAILLEAU Eric <>
Tue Jan 1 11:43:41 CET 2019


Hi,


1> c(floaty).
{ok,floaty}
2> floaty:auto(12.345555).
"12.345555"
3> floaty:auto(12.3455553333333).
"12.3455553333333"
4> list_to_float(floaty:auto(12.3455553333333)).
12.3455553333333




Le 31/12/2018 à 20:31, Dan Sommers a écrit :
> On 12/31/18 10:37 AM, Vans S wrote:
> 
>  > > 1> 0.0001.
>  > 0.0001
>  > > 2> 0.00001.
>  > 1.0e-5
> 
>  > Once floats get to the 4th/5th decimal place they start being
>  > displayed with the e-x notation.  Is there a way to make them always
>  > display "normally", for example 0.00001 in this case ...
> 
> At some point, it's shorter and easier to read with the e-x notation.
> 
> Consider a number like 1e-44.  The last thing I want is to have to count
> all those zeros.  ;-)
> 
> But you probably knew that.
> 
>  > ... The problem is when you turn the float into a string, its also
>  > displayed as 1.0e-5, adding a format function works yes, but gets
>  > annoying to maintain when you need to do arithmetic on the floats.
>  > LIke sorting by the value.
> 
> I'm confused:  if you're doing arithmetic on the floats, why are you
> concerned with the strings?
> 
> If you're sorting the strings, then you'll probably either (a) have to
> ensure a consistent format, perhaps with something like a ~24.18.0e
> specifier, or (b) convert the strings back to floats and suffer various
> rounding errors.
> 
>  > Also debugging becomes annoying when you see the e-5, e-6, etc
>  > notation everywhere and have to match it up.
> 
> On that we agree.  :-)
> 
>  > Is there a way to compile / add arg to the VM to not do this?
> 
> I'm pretty new at Erlang, so I'm probably missing a lot, but how are you
> displaying the values now if not with a format function?  (I guess
> there's io:write, but at that point, you're awfully close to calling
> io:fwrite anyway.)
> 
> Are you just using the shell to do immediate calculations?  I'm sure
> that the shell has its own default formatting, or maybe it just calls
> io:write.
> 
> Dan
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> 

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