[dart-misc] set global default double -> string precision

Discussion:

Rich Eakin

2015-07-12 22:20:59 UTC

I've been working on a simulation in dart and found the double.
toStringAsFixed() method very useful in controlling how much data gets
printout to console when I'm debugging variables. I was thinking though, it
would be nice if it was possible to set a global precision for my
application or isolate, so that I did not have to write that method in
every print statement that I make. Is there any existing discussion for
something like this, or a feature request?

cheers,
Rich

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'Lasse R.H. Nielsen' via Dart Misc

2015-07-13 09:14:29 UTC

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Not any request or discussion that I can remember.

If you have a fixed format that you tend to use, you could use a helper
function to do the formatting for you:

int fixedPrecision = 3;
String toFixed(double value) => value.toStringAsFixed(fixedPrecision);

We don't have any printf, which is what you would normally use in other
languages, because string interpolations does most of the job very well.
A case that it doesn't handle as well is number formatting, which gets
pretty verbose.

/L

Post by Rich Eakin
I've been working on a simulation in dart and found the double.
toStringAsFixed() method very useful in controlling how much data gets
printout to console when I'm debugging variables. I was thinking though, it
would be nice if it was possible to set a global precision for my
application or isolate, so that I did not have to write that method in
every print statement that I make. Is there any existing discussion for
something like this, or a feature request?
cheers,
Rich
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--
Lasse R.H. Nielsen - ***@google.com
'Faith without judgement merely degrades the spirit divine'
Google Denmark ApS - Frederiksborggade 20B, 1 sal - 1360 KÃžbenhavn K
- Denmark - CVR nr. 28 86 69 84

k***@gmail.com

2015-07-13 10:53:33 UTC

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<html><head></head><body lang="zh-TW" style="background-color: rgb(255, 255, 255); line-height: initial;"> <div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Adopt log library and extend it with your own implementation</div> <div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br style="display:initial"></div> <div style="font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div> <table width="100%" style="background-color:white;border-spacing:0px;"> <tbody><tr><td colspan="2" style="font-size: initial; text-align: initial; background-color: rgb(255, 255, 255);"> <div style="border-style: solid none none; border-top-color: rgb(181, 196, 223); border-top-width: 1pt; padding: 3pt 0in 0in; font-family: Tahoma, 'BB Alpha Sans', 'Slate Pro'; font-size: 10pt;"> <div><b>寄件者： </b>'Lasse R.H. Nielsen' via Dart Misc</div><div><b>已傳送： </b>2015年7月13日星期一 17:14</div><div><b>收件者： </b>***@dartlang.org</div><div><b>回覆至： </b>***@dartlang.org</div><div><b>主旨： </b>Re: [dart-misc] set global default double -> string precision</div></div></td></tr></tbody></table><div style="border-style: solid none none; border-top-color: rgb(186, 188, 209); border-top-width: 1pt; font-size: initial; text-align: initial; background-color: rgb(255, 255, 255);"></div><br><div id="_originalContent" style=""><div dir="ltr">Not any request or discussion that I can remember.<div><br></div><div>If you have a fixed format that you tend to use, you could use a helper function to do the formatting for you:</div><div><br></div><div>int fixedPrecision = 3;</div><div>String toFixed(double value) => value.toStringAsFixed(fixedPrecision);</div><div><br></div><div>We don't have any printf, which is what you would normally use in other languages, because string interpolations does most of the job very well.</div><div>A case that it doesn't handle as well is number formatting, which gets pretty verbose.</div><div><br></div><div>/L</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Jul 13, 2015 at 12:20 AM, Rich Eakin <span dir="ltr"><<a href="mailto:***@gmail.com" target="_blank">***@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">I've been working on a simulation in dart and found the double.<span>toStringAsFixed</span>() method very useful in controlling how much data gets printout to console when I'm debugging variables. I was thinking though, it would be nice if it was possible to set a global precision for my application or isolate, so that I did not have to write that method in every print statement that I make. Is there any existing discussion for something like this, or a feature request?<div><br></div><div>cheers,</div><div>Rich  </div></div><span class="HOEnZb"><font color="#888888">

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</font></span></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature">Lasse R.H. Nielsen - <a href="mailto:***@google.com" target="_blank">***@google.com</a>  <div>'Faith without judgement merely degrades the spirit divine'<br><font size="1" color="#999999">Google Denmark ApS - Frederiksborggade 20B, 1 sal - 1360 København K - Denmark - CVR nr. 28 86 69 84</font></div></div>
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Ian Mackenzie

2015-07-14 03:53:47 UTC

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If you're not using string interpolation and just calling print(someValue),
then perhaps you could use a Zone
<https://www.dartlang.org/articles/zones/#example-overriding-print> to
override the print() function within a body of code to recognize doubles
and format them to a given precision? You could even get fancy with your
overridden print() function to allow passing it lists of arguments, and it
would concatenate the string versions of each while using your default
precision for doubles, so you could call (within the zone)

print(['The value of x is ', x, ' and the value of y is ', y]);

to get a form of string interpolation (unless of course you also want to be
able to print out lists as lists!).

Rich Eakin

2015-07-15 23:13:48 UTC

Permalink

The zones is an interesting idea. Ideally though, I think it would be nice
to use the built in print function or a custom function that took the same
parameter (Object), and control how the formatting is done. The problem
with using my own custom print function (or a logging library for that
matter), is that as far as I can tell the double.toString()'s have already
happened so my function only sees a big concatenated string.

Post by Ian Mackenzie
If you're not using string interpolation and just calling
print(someValue), then perhaps you could use a Zone
<https://www.dartlang.org/articles/zones/#example-overriding-print> to
override the print() function within a body of code to recognize doubles
and format them to a given precision? You could even get fancy with your
overridden print() function to allow passing it lists of arguments, and it
would concatenate the string versions of each while using your default
precision for doubles, so you could call (within the zone)
print(['The value of x is ', x, ' and the value of y is ', y]);
to get a form of string interpolation (unless of course you also want to
be able to print out lists as lists!).

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For HOWTO questions, visit http://stackoverflow.com/tags/dart
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Ian Mackenzie

2015-07-16 03:43:33 UTC

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Well, I suppose if your custom print function gets passed a string, you
could use a regular expression to find all substrings that look like
printed double values, then parse those as doubles, convert them back to
strings using your desired precision, then rebuild the argument string
based on them before actually printing it...but of course that only works
if you're looking to *decrease* precision from the default and would break
if you ever tried to print something like "version 2.3".

Post by Rich Eakin
The zones is an interesting idea. Ideally though, I think it would be nice
to use the built in print function or a custom function that took the same
parameter (Object), and control how the formatting is done. The problem
with using my own custom print function (or a logging library for that
matter), is that as far as I can tell the double.toString()'s have already
happened so my function only sees a big concatenated string.

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