Changing the precision of a double

Peace

Folks,

I'm hoping this is a simple or stupid question... I need to change the precision that a double shows on screen. I want to force it always to be 2 decimal places shown.

I've checked msdn... no mention... googled... no joy. I remember being able to do it in C with floats.... how about it lads?

----

I'm using C# with ... .Net 1.1 (i think)

king_of_inismac

Ok, heres what I'd do.

//variables
char tempString[30];
double temp = 50;

//this converts the double to a string with 2 decimal places

sprintf(&tempString,"%1.2f", temp);

//display tempstring to the display//




Hope this helps!,

Martin

str8_away

There is no stupid question as I always say.

You could try "round" function.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemdecimalclassroundtopic.asp

Hope this helps

leeroybrown

The sprintf solution will probably (I don't use C# so I'm not sure) truncate the double after the second decimal place so 2.099 should become 2.09.

The round solution gives a correctly rounded number but the result will only have decimal places if they exist. 2.099 will round to 2.1 which won't print with two decimals without a sprintf.

If sprintf truncates the double, then it's probably best to sprintf a round'ed double if you want the best of both worlds.

bonkey

Oof.

Easy to see there's no C# programmer answered it yet ;

Peace...have a look at the ToString overrides available on the double (and/or Double) types.

You will see that as well as :

myDouble.ToString()

you can also have

myDouble.ToString(formatString)

There are also more complex options which allow you to do all sorts of funky items, but you shouldn't need much.

What should do it for you is :

myDouble.ToString("0.00");

This will guarantee one place before and two places after the decimal place. Strangely, to the left of hte decimal place, 0's simply define the *minimum* number of places to display, where as to the right of it they define the *absolute* number of places to display.

Thus, the following code :

double d = 2000.123;
Console.WriteLine(d.ToString("0.00"));

Will produce as its output :

2000.12

Ta-dah!

I'd strongly suggest you check up on the formatting options in C# because this is central to effective data-presentation.

Cheers,

jc

bonkey

Oh...the formatting does auto-rounding as well in the usual manner. .5 and up will get rounded up, otherwise round down.

So in my example before, if I changed the test-value from 200.123 to 2000.125, the output would be 2000.13.

jc

ressem

Nope, no sprintf in c#.

For this, look at the double.ToString() method.
Can take an IFormatProvider class as a parameter.
You're looking to use NumberFormatInfo.

Slightly modified version of the MSDN sam ple.

As you can tell, lets you fob off some regionalization stuff to Microsoft.

Edit, to compare to Bonkey's method
This uses filler 0's if it needs to at the end.
It automatically rounds in the standard way.

Advantage in being able to change precision in one place for the entire class. Same for currency, thousands markers etc. Too easy to skimp on.

/Edit


using System;
using System.Globalization;

class NumberFormatInfoSample {

public static void Main() {
// Gets a NumberFormatInfo associated with the en-US culture.
NumberFormatInfo nfi = new CultureInfo( "en-US", false ).NumberFormat;

// Displays a negative value with the default number of decimal digits 2.
double myDouble = 3.14159265358979323846;
Console.WriteLine( myDouble.ToString( "N", nfi ) );

// Displays the same value with four decimal digits.
nfi.NumberDecimalDigits = 4;
Console.WriteLine( myDouble.ToString( "N", nfi ) ); }
}

Peace

Originally posted by bonkey
Oof.

Easy to see there's no C# programmer answered it yet ;

Peace...have a look at the ToString overrides available on the double (and/or Double) types.

You will see that as well as :

myDouble.ToString()

you can also have

myDouble.ToString(formatString)

There are also more complex options which allow you to do all sorts of funky items, but you shouldn't need much.

What should do it for you is :

myDouble.ToString("0.00");

This will guarantee one place before and two places after the decimal place. Strangely, to the left of hte decimal place, 0's simply define the *minimum* number of places to display, where as to the right of it they define the *absolute* number of places to display.

Thus, the following code :

double d = 2000.123;
Console.WriteLine(d.ToString("0.00"));

Will produce as its output :

2000.12

Ta-dah!

I'd strongly suggest you check up on the formatting options in C# because this is central to effective data-presentation.

Cheers,

jc

Nailed it... nice one

Cheers everybody....

Evil Phil

God I love C#. Haven't seen CultureInfo and related classes being used before but I'll be using them from now on