If you begin by writing Raul's idea as an explicit definition, J selects a
different choice than his version. However, you can write and explicit
definition to produce his verb.
f=: 13 :'":".y'
g=: 13 :'":&".y'
f
[: ": ".
g
":&".
f 'z' [z=: 5.13e7
51300000
g 'z' [z=: 5.13e7
51300000
Linda
-----Original Message-----
From: programming-boun...@forums.jsoftware.com
[mailto:programming-boun...@forums.jsoftware.com] On Behalf Of Ian Clark
Sent: Tuesday, August 25, 2015 11:05 PM
To: programm...@jsoftware.com
Subject: Re: [Jprogramming] Format a floating number without rounding errors
I guess you mean:
format=: ":&".
So simple. And here was me fooling around with 0j300&": and all sorts.
(I had a blind spot from using 5!:5 to handle a much wider range of
datatypes.)
On Wed, Aug 26, 2015 at 3:55 AM, 'Pascal Jasmin' via Programming
<programm...@jsoftware.com> wrote:
> ": seems to work with all your examples, and does 6 decimal places
automagically.
>
>
> ----- Original Message -----
> From: Ian Clark <earthspo...@gmail.com>
> To: programm...@jsoftware.com
> Cc:
> Sent: Tuesday, August 25, 2015 10:41 PM
> Subject: [Jprogramming] Format a floating number without rounding
> errors
>
> Can anyone tell me how to define a verb: format which returns a
> numeral string for a noun z of datatype: 'floating' which is formally
> identical to the original definition of z, viz
>
> format 'z' [z=: 5.13
> 5.13
> format 'z' [z=: 5.13e_7
> 5.13e_7
> format 'z' [z=: 5e_7
> 5e_7
> format 'z' [z=: 5e_4
> 0.0005
>
> Hitherto I've been using 5!:5 -which gives (or exposes) rounding
> errors
>
> format=: 5!:5&<
> format 'z' [z=: 5.13
> 5.12999999999999989
> format 'z' [z=: 5.13e_7
> 5.13000000000000001e_7
> format 'z' [z=: 5e_7
> 4.99999999999999977e_7
> format 'z' [z=: 5e_4
> 0.00050000000000000001
>
> I want it to work with the full range of exponents and up to 6 decimal
> places (say) of mantissa.
>
> JVERSION
> Engine: j803/2014-10-19-11:11:11
> Library: 8.03.13
> Qt IDE: 1.3.1/5.3.2
> Platform: Darwin 64
> Installer: J803 install
> InstallPath: /applications/j64-803
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