Comments on: Using floating point variables to represent money => not a good idea! http://jamescrisp.org/2007/02/25/using-floating-point-variables-to-represent-money-not-a-good-idea/ C#, .NET, Ruby, Rails, book reviews, mind hacks, Wing Chun and the occasional personal bit. Fri, 18 May 2012 00:35:26 +0000 hourly 1 http://wordpress.org/?v=3.3.2 By: James http://jamescrisp.org/2007/02/25/using-floating-point-variables-to-represent-money-not-a-good-idea/#comment-9537 James Wed, 10 Dec 2008 06:54:10 +0000 http://jamescrisp.org/wordpress/?p=42#comment-9537 Thanks Michael, the title of this post should really be "Using _base 2_ floating point variables to represent money => not a good idea! Thanks Michael, the title of this post should really be "Using _base 2_ floating point variables to represent money => not a good idea!

]]> By: Michael Skelton http://jamescrisp.org/2007/02/25/using-floating-point-variables-to-represent-money-not-a-good-idea/#comment-9535 Michael Skelton Tue, 09 Dec 2008 18:15:24 +0000 http://jamescrisp.org/wordpress/?p=42#comment-9535 The .NET decimal type is still a floating-point numeric, as it uses a variable scaling factor. It is the fact that the implied base of decimal's scaling factor is 10 (not 2) that exempts it from the accuracy limitations of the other floating-point data types in representing "real" numbers. The .NET decimal type is still a floating-point numeric, as it uses a variable scaling factor. It is the fact that the implied base of decimal's scaling factor is 10 (not 2) that exempts it from the accuracy limitations of the other floating-point data types in representing "real" numbers.

]]> By: James http://jamescrisp.org/2007/02/25/using-floating-point-variables-to-represent-money-not-a-good-idea/#comment-113 James Wed, 22 Aug 2007 11:52:05 +0000 http://jamescrisp.org/wordpress/?p=42#comment-113 Hi Ryan, You could multiply the number by 10 to the power of the number of decimal places you are interested in, truncate the result and then divide it by the number of decimal places you are interested in. Eg, (x * 10000).truncate() / 10000. Cheers, James Hi Ryan,

You could multiply the number by 10 to the power of the number of decimal places you are interested in, truncate the result and then divide it by the number of decimal places you are interested in. Eg, (x * 10000).truncate() / 10000.

Cheers,
James

]]> By: samar massaad http://jamescrisp.org/2007/02/25/using-floating-point-variables-to-represent-money-not-a-good-idea/#comment-111 samar massaad Tue, 21 Aug 2007 07:36:03 +0000 http://jamescrisp.org/wordpress/?p=42#comment-111 what is the namespace for the currency variable what is the namespace for the currency variable

]]> By: Anonymous http://jamescrisp.org/2007/02/25/using-floating-point-variables-to-represent-money-not-a-good-idea/#comment-67 Anonymous Tue, 29 May 2007 02:58:00 +0000 http://jamescrisp.org/wordpress/?p=42#comment-67 Using C#: You wouldn't happen to know a nice way to truncate down from 7 decimal to 4 decimal places for example. <br/><br/>All the Decimal members (in .NET 2.0) add a rounding aspect to any return values or only consider the integer component or round up. <br/><br/>We see the options as:-<br/>1. A small amount of arithmetic to 'construct' the correct output. (E.g. maybe rounding and then 'if' either subtract or add a delta.)<br/><br/>2. Casting to a string and then manipulating and then casting sub strings back.<br/><br/>Neither of the above fell elegant though. <br/><br/>P.S. Great blog, I'll be back to have a bit more of read especially the book reviews.<br/><br/>Cheers<br/>Ryan Using C#: You wouldn't happen to know a nice way to truncate down from 7 decimal to 4 decimal places for example.

All the Decimal members (in .NET 2.0) add a rounding aspect to any return values or only consider the integer component or round up.

We see the options as:-
1. A small amount of arithmetic to 'construct' the correct output. (E.g. maybe rounding and then 'if' either subtract or add a delta.)

2. Casting to a string and then manipulating and then casting sub strings back.

Neither of the above fell elegant though.

P.S. Great blog, I'll be back to have a bit more of read especially the book reviews.

Cheers
Ryan

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