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PODRY without having single code?
 

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  1. PODRY without having single code?
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    <p>i want to not repeat myself (DRY), but i cannot have a single piece of code. For example here is code repeated 3 times with the same bug:</p> <pre><code>class StarWars : Movie { //Calculate "base ^ exponent" public float Power(float base, float exponent) { return (base * exponent); } } class Customer: Object { //Calculate "base ^ exponent" public float Exponential(float base, float exponent) { return (base ^ exponent); } } class Student: Person { //Calculate "base ^ exponent" public float CalculateExpoential(float base, float exponent) { return CalculateExponential(2.7182818, exponent * Ln(base)); } } </code></pre> <p>Now ideally i would have extracted this common function into it's own helper somewhere:</p> <pre><code>class LibraryOfHelperCode { public static float Exponentiation(float base, float exponent) { return Exp(2.71828183, base * Ln(exponent)); } } </code></pre> <p>And converted the existing code to use it:</p> <pre><code>class StarWars : Movie { //Calculate "base ^ exponent" public float Power(float base, float exponent) { return LibraryOfHelperCode.Exponentiation(base, exponent); } } class Customer: Object { //Calculate "base ^ exponent" public float Exponential(float base, float exponent) { return LibraryOfHelperCode.Exponentiation(base, exponent); } } class Student: Person { //Calculate "base ^ exponent" public float CalculateExpoential(float base, float exponent) { return LibraryOfHelperCode.Exponentiation(base, exponent); } } </code></pre> <p>The value is that now i've extracted the repeated code from </p> <ul> <li>Power</li> <li>Exponential</li> <li>CalculateExpoential</li> </ul> <p>into a single function. This means that if there are any bugs, they only have to be fixed once. Which is good in this case, because there <strong>is</strong> a bug:</p> <pre><code> public float CalculateExpoential(float base, float exponent) { //19971012: Oops, should be natrual log of base, not exponent return Exp(2.71828183, exponent * Ln(base)); } </code></pre> <p>and a few years after that:</p> <pre><code> public float CalculateExpoential(float base, float exponent) { //19990321: Oops, need to handle when exponent is zero if (exponent == 0) return 1.0; //19971012: Oops, should be natrual log of base, not exponent return Exp(2.71828183, exponent * Ln(base)); } </code></pre> <p>and later on:</p> <pre><code> public float CalculateExpoential(float base, float exponent) { //19990321: Oops, need to handle when exponent is zero if (exponent == 0) return 1.0; //20040523: Another special case if (Base = 0.0) &amp;&amp; (Exponent &gt; 0.0) then return 0.0; // 0**n = 0, n &gt; 0 //19971012: Oops, should be natrual log of base, not exponent return Exp(2.71828183, exponent * Ln(base)); } </code></pre> <p>and finally:</p> <pre><code> public float CalculateExpoential(float base, float exponent) { //20101027: Microsoft just release a method in .NET framework 4.0 that does //what we need. Use it: return Math.Pow(base, exponent); } </code></pre> <p>And everyone gets the fixes. On the other hand, i cannot guarantee that any one of those increment fixes won't break existing code. </p> <p><em>Imagine</em> a guy was calling:</p> <pre><code>char ps = Math.Trunc(Exponential(ProblemSize, ProblemComplexity)); </code></pre> <p>and was never expecting the value to be larger than 128. He was wrong. And while the code was <strong>wrong</strong> all this time: it <strong>happened</strong> to work.</p> <p>Now i come along and <em>fix</em> things, and suddenly code is crashing due to overflow and/or wraparound.</p> <hr> <p>The problem i'm facing today is that a change in DRY common code affects everywhere it's used. The only acceptable (polotical) solution is to keep a copy of the library class for every executable/moduble/namespace/class that uses it.</p> <p>Undoing any DRYness.</p> <p>Is there any way out of this mess? When i can not repeat myself, but continue to get fixes and improvements as they are added to the single DRY code?</p> <hr> <p>i mean...should i have shared code, but branch it at every release? But the issue that is polotically nobody wants the code every to be reverse-integrated.</p>
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    1. COYour rather long-winded example doesn't seem to have anything to do with your actual question about libraries. In your example the obvious answer is "use inheritance".
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      1. USmeagar
    2. COSounds like you know the right technological solution, but the politics of your job prevent you from doing it. Perhaps it's time to start looking for a new job?
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    3. CO@meagar What do you mean *use inheritance*? What do you mean that the code has nothing to do with libraries? Rename `Helper` to `Library` and might become clearer.
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      1. USIan Boyd
 

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