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PO
 

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  1. PO
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    <p>Floats aren't stable for accumulating and decrementing funds. Here's your actual example:</p> <pre><code>using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace BadFloat { class Program { static void Main(string[] args) { Currency yourMoneyAccumulator = 0.0d; int count = 200000; double increment = 20000.01d; //1 cent for (int i = 0; i &lt; count; i++) yourMoneyAccumulator += increment; Console.WriteLine(yourMoneyAccumulator + " accumulated vs. " + increment * count + " expected"); } } struct Currency { private const double EPSILON = 0.00005; public Currency(double value) { this.value = value; } private double value; public static Currency operator +(Currency a, Currency b) { return new Currency(a.value + b.value); } public static Currency operator -(Currency a, Currency b) { return new Currency(a.value - b.value); } public static Currency operator *(Currency a, double factor) { return new Currency(a.value * factor); } public static Currency operator *(double factor, Currency a) { return new Currency(a.value * factor); } public static Currency operator /(Currency a, double factor) { return new Currency(a.value / factor); } public static Currency operator /(double factor, Currency a) { return new Currency(a.value / factor); } public static explicit operator double(Currency c) { return System.Math.Round(c.value, 4); } public static implicit operator Currency(double d) { return new Currency(d); } public static bool operator &lt;(Currency a, Currency b) { return (a.value - b.value) &lt; -EPSILON; } public static bool operator &gt;(Currency a, Currency b) { return (a.value - b.value) &gt; +EPSILON; } public static bool operator &lt;=(Currency a, Currency b) { return (a.value - b.value) &lt;= +EPSILON; } public static bool operator &gt;=(Currency a, Currency b) { return (a.value - b.value) &gt;= -EPSILON; } public static bool operator !=(Currency a, Currency b) { return Math.Abs(a.value - b.value) &lt;= EPSILON; } public static bool operator ==(Currency a, Currency b) { return Math.Abs(a.value - b.value) &gt; EPSILON; } public bool Equals(Currency other) { return this == other; } public override int GetHashCode() { return ((double)this).GetHashCode(); } public override bool Equals(object other) { return other is Currency &amp;&amp; this.Equals((Currency)other); } public override string ToString() { return this.value.ToString("C4"); } } } </code></pre> <p>On my box this gives $4,000,002,000.0203 accumulated vs. 4000002000 expected in C#. It's a bad deal if this gets lost over many transactions in a bank - it doesn't have to be large ones, just many. Does that help?</p>
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    1. POWhy is using a NON-decimal data type bad for money?
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    1. PTAnswer
    1. USJ Trana
    1. USJ Trana
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    1. POWhy is using a NON-decimal data type bad for money?
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      1. VTUpMod
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    1. COI don't see the word `Currency` anywhere... did you read the question? -1
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      1. USMehrdad
    2. COYou've missed the point of the question. If you use OP's struct, you wouldn't have that problem.
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      1. UScorsiKa
    3. COYour example might have more substance if it used `double` as Mehrdad did in his Currency class. ;)
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      1. USJeff Mercado
 

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