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Merge pull request #180 from skvadrik/master

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Clarify how lazy evaluation helps to escape infinite co-recursion.
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Sergei Trofimovich 2022-06-02 17:39:44 +00:00 committed by GitHub
parent 47bde1fda3 36252cb882
commit a2a1262326
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pills/13-callpackage-design-pattern.xml
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@ -115,7 +115,7 @@
Note how easy is to override arguments in the case of <package>graphviz</package> without <package>gd</package>. But most importantly, how easy it was to merge two repositories: <literal>nixpkgs</literal> and our <literal>pkgs</literal>!
</para>
<para>
The reader should notice a magic thing happening. We're defining <literal>pkgs</literal> in terms of <literal>callPackage</literal>, and <literal>callPackage</literal> in terms of <literal>pkgs</literal>. That magic is possible thanks to lazy evaluation.
The reader should notice a magic thing happening. We're defining <literal>pkgs</literal> in terms of <literal>callPackage</literal>, and <literal>callPackage</literal> in terms of <literal>pkgs</literal>. That magic is possible thanks to lazy evaluation: <literal>builtins.intersectAttrs</literal> doesn't need to know the values in <literal>allPkgs</literal> in order to perform intersection, only the keys that do not require <literal>callPackage</literal> evaluation.
</para>
</section>
<section>