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Use transparent comparators for StringMap and StringPairs

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Sergei Zimmerman 2025-05-19 20:38:19 +00:00
parent 8ee513379a
commit 49d026083b
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1 changed files with 19 additions and 2 deletions
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21
src/libutil/include/nix/util/types.hh
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@ -12,8 +12,25 @@
namespace nix {
typedef std::list<std::string> Strings;
typedef std::map<std::string, std::string> StringMap;
typedef std::map<std::string, std::string> StringPairs;
/**
* Alias to ordered std::string -> std::string map container with transparent comparator.
*
* Used instead of std::map<std::string, std::string> to use C++14 N3657 [1]
* heterogenous lookup consistently across the whole codebase.
* Transparent comparators get rid of creation of unnecessary
* temporary variables when looking up keys by `std::string_view`
* or C-style `const char *` strings.
*
* [1]: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3657.htm
*/
using StringMap = std::map<std::string, std::string, std::less<>>;
/**
* Alias to an ordered map of std::string -> std::string. Uses transparent comparator.
*
* @see StringMap
*/
using StringPairs = StringMap;
/**
* Alias to ordered set container with transparent comparator.