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| 43 | How to control properties order? |
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| 44 | </h2></div></div></div> |
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| 45 | <p>For internal reasons, Boost.Build sorts all the properties |
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| 46 | alphabetically. This means that if you write: |
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| 47 | </p> |
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| 48 | <pre class="programlisting"> |
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| 49 | exe a : a.cpp : <include>b <include>a ; |
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| 50 | </pre> |
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| 51 | <p> |
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| 52 | then the command line with first mention the "a" include directory, and |
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| 53 | then "b", even though they are specified in the opposite order. In most |
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| 54 | cases, the user doesn't care. But sometimes the order of includes, or |
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| 55 | other properties, is important. For example, if one uses both the C++ |
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| 56 | Boost library and the "boost-sandbox" (libraries in development), then |
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| 57 | include path for boost-sandbox must come first, because some headers may |
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| 58 | override ones in C++ Boost. For such cases, a special syntax is |
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| 59 | provided: |
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| 60 | </p> |
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| 61 | <pre class="programlisting"> |
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| 62 | exe a : a.cpp : <include>a&&b ; |
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| 63 | </pre> |
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| 64 | <p>The <code class="computeroutput">&&</code> symbols separate values of an |
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| 65 | property, and specify that the order of the values should be preserved. You |
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| 66 | are advised to use this feature only when the order of properties really |
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| 67 | matters, and not as a convenient shortcut. Using it everywhere might |
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| 68 | negatively affect performance. |
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